Crystallization apparatus, crystallization method, phase modulation element, device and display apparatus

ABSTRACT

A phase modulation element according to the present invention has a first area having a first phase value based on a phase modulation unit having a predetermined size and a second area having a second phase value based on the phase modulation unit having the predetermined size, and each phase distribution is defined by a change in area shares of the first area and the second area depending on each position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of application Ser. No.10/790,828, filed Mar. 3, 2004, and is based upon and claims the benefitof priority from prior Japanese Patent Application No. 2003-117486,filed Apr. 22, 2003. The entire contents of the above-identifiedapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a crystallization apparatus, acrystallization method, a phase modulation element, a device and adisplay apparatus used to generate a crystallized semiconductor film byirradiating a polycrystal semiconductor film or an amorphoussemiconductor film with laser beams having a predetermined lightintensity.

2. Description of the Related Art

For example, a thin film transistor (TFT) used for, e.g., a switchingelement which controls a voltage applied to pixels in a liquid crystaldisplay (LCD) is formed on an amorphous silicon layer or a polysiliconlayer.

The polysilicon layer has a higher mobility of electrons or electronholes than that of the amorphous silicon layer. Therefore, when atransistor is formed on the polysilicon layer, a switching speed isincreased and a response speed of a display is improved as compared witha case that a transistor is formed on the amorphous silicon layer.

Further, a peripheral LSI can be constituted of a thin film transistor.Furthermore, there is an advantage that a design margin of any othercomponent can be reduced. Moreover, when peripheral circuits such as adriver circuit or a DAC are incorporated in a display, these peripheralcircuits can be operated at a higher speed.

Although the polycrystal silicon is formed of an aggregation of crystalgrains, it has a lower mobility of electrons or electron holes than thatof single crystal silicon. Additionally, many thin film transistorsformed on the polycrystal silicon have a problem of irregularities incrystal grain boundary number in a channel portion. Thus, in order toimprove the mobility of electrons or electron holes and reduceirregularities in crystal grain boundary number in the channel portion,there has been proposed a crystallization method which generatescrystallized silicon with a large grain size.

As this type of crystallization method, there is known a “phase controlELA (Excimer Laser Annealing) method) which generates a crystallizedsemiconductor film by irradiating a phase shifter approximated to apolycrystal semiconductor film or an amorphous semiconductor film inparallel with excimer laser beams. The detail of the phase control ELAmethod is disclosed in, e.g., “Surface Science Vol. 21, No. 5, pp.278-287, 2000”.

In the phase control ELA method, a light intensity distribution with aninverse peak pattern (pattern that a light intensity is substantiallyzero at the center and the light intensity is suddenly increased towardthe periphery) that a light intensity is substantially zero at a pointcorresponding to a phase shift portion of a phase shifter is generated,and a polycrystal semiconductor film or an amorphous semiconductor filmis irradiated with light beams having this light intensity distributionwith the inverse peak pattern. As a result, a temperature gradient isgenerated in a fusion area in accordance with the light intensitydistribution, a crystal nucleus is formed at a part which is solidifiedfirst in accordance with a point where the light intensity issubstantially zero, and a crystal grows in the lateral direction fromthe crystal nucleus toward the periphery (which will be referred to as a“lateral growth” or a “lateral-directional growth” hereinafter), therebyproducing single crystal grains with a large particle size.

Additionally, Jpn. Pat. Appln. KOKAI Publication No. 2000-306859discloses a technique to perform crystallization by irradiating asemiconductor film with light beams having a light intensitydistribution with an inverse peak pattern generated through a phaseshift mask (phase shifter).

Further, “Amplitude of Silicon Thin Film/Phase Control Excimer LaserFusion Recrystallization Method—New 2-D Position-controlled LargeCrystal Grain Forming Method—”, Inoue, Nakata and Matsumura, Theinstitute of Electronics, Information and Communication EngineersTransactions Vol. J85-C, No. 8, pp. 624-629, August 2002 discloses atechnique to perform crystallization by irradiating a semiconductor filmwith light beams having a light intensity including a concave patternand an inverse pattern generated by combining a phase shifter and alight absorption distribution (see FIG. 3 and a relevant description).

As disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-306859,according to the technique to form a light intensity distribution withan inverse peak pattern by using a phase shifter, the light intensitydistribution with the inverse peak pattern is formed at a partcorresponding to a phase shift portion. However, since the lightintensity is not linearly increased and an additional irregulardistribution is generated around the light intensity distribution withthe inverse peak pattern, the growth of the crystal is apt to befinished halfway.

It is to be noted that the obtained light intensity distribution may bepossibly caused to approximate an ideal distribution by adjusting anangle distribution of illumination light beams relative to the phaseshifter or designing an arrangement position of the phase shifter.However, that design cannot be analytically performed with aperspective, and it can be expected that very complicated designconditions are given even if the analytic design can be realized.

On the other hand, as disclosed in The institute of Electronics,Information and Communication Engineers Transactions, according to thetechnique in which the phase shifter is combined with the lightabsorption distribution, a light intensity distribution with the concavepattern and the inverse peak pattern for crystallization can beobtained. However, it is difficult to realize this distribution. Thatis, forming a film having a light absorption distribution whichcontinuously varies is generally difficult. Further, light beams havinga very strong intensity for crystallization is undesirable since ittends to generate a deterioration in a film material of a film having alight absorption distribution due to heat from light absorption or achemical change when a film to be crystallized is irradiated.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a crystallizationapparatus which can generate a crystallized semiconductor film with alarge grain size by causing a crystal to grow in the lateral directionfrom a crystal nucleus, a crystallization method, a thin film transistorusing a crystallized semiconductor film and a display apparatus.

According to an aspect of the present invention, there is provided acrystallization apparatus comprising: a phase modulation element inwhich a phase of outgoing light beams relative to incident light beamsdiffers depending on each position; an illumination system used togenerate the incident light beams which enter the phase modulationelement; an image formation optical system provided on an outgoingradiation side of the phase modulation element; and a stage used tosupport a substrate having a non-single crystal semiconductor filmprovided on an outgoing radiation side of the image formation opticalsystem, wherein the phase modulation element has a phase distributionbased on a phase modulation unit which is optically smaller than aradius of a point spread distribution range of the image formationoptical system when converted to an image formation surface of the imageformation optical system.

According to another aspect of the present invention, there is providedan exposure apparatus comprising: a phase modulation element in which aphase of outgoing light beams relative to incident light beams differsdepending on each position; an illumination system used to generate theincident light beams which enter the phase modulation element; an imageformation optical system provided on an outgoing radiation side of thephase modulation element; and an image formation optical system arrangedin a light path between the phase modulation element and a predeterminedsurface, wherein the phase modulation element has a phase distributionbased on a phase modulation unit which is optically smaller than aradius of a point spread distribution range of the image formationoptical system when converted to an image formation surface of the imageformation optical system.

According to still another aspect of the present invention, there isprovided a crystallization method comprising: illuminating a phasemodulation element having a phase distribution based on a phasemodulation unit which is optically smaller than a radius of a pointspread distribution range of an image formation optical system whenconverted to an image formation surface; and irradiating a polycrystalsemiconductor film or an amorphous semiconductor film with light beamshaving a predetermined light intensity distribution through the imageformation optical system arranged in a light path between the phasemodulation element and the polycrystal semiconductor film or theamorphous semiconductor film, thereby generating a crystallizedsemiconductor film.

According to a further aspect of the present invention, there isprovided a crystallization method comprising: illuminating a phasemodulation element having a phase distribution based on a phasemodulation unit which is optically smaller than a radius of a pointspread distribution range of an image formation optical system whenconverted to an image formation surface; and forming a predeterminedlight intensity distribution on a predetermined surface through theimage formation optical system arranged in a light path between thephase modulation element and the predetermined surface.

According to a still further aspect of the present invention, there isprovided a phase modulation element having a phase distribution based ona phase modulation unit having a predetermined size, comprising: a firstarea having a first phase value; and a second area having a second phasevalue, wherein the phase distribution is defined by a change in areashares of the first area and the second area depending on each position.

According to a still further aspect of the present invention, there isprovided a phase modulation element having a phase distribution based ona phase modulation unit having a predetermined size, comprising:

a plurality of divided areas each having a fixed phase value, whereineach of the divided areas has a phase distribution that the phase valuecyclically varies in accordance with each divided area.

According to a still further aspect of the present invention, there isprovided a phase modulation element having a phase distribution based ona phase modulation unit having a predetermined size, comprising: a firststripe-like area which has a first phase distribution and extends in adirection along which a phase varies; and a second stripe-like areawhich has a second phase distribution and extends in the direction alongwhich the phase varies, wherein the first stripe-like area and thesecond stripe-like area are adjacent to each other with a border lineparallel with the direction along which the phase varies therebetween,and an average phase value on the first stripe-like area side issubstantially different from an average phase value on the secondstripe-like area side in a local area on the border line.

According to a still further aspect of the present invention, there isprovided a device comprising:

a semiconductor film manufactured by a crystallization method, thecrystallization method comprising: illuminating a phase modulationelement having a phase distribution based on a phase modulation unitwhich is optically smaller than a radius of a point spread distributionrange of an image formation optical system when converted to an imageformation surface; and forming a predetermined light intensitydistribution on a predetermined surface through the image formationoptical system arranged in a light path between the phase modulationelement and the predetermined surface.

According to a still further aspect of the present invention, there isprovided a display apparatus comprising: a pair of substrates joined toeach other with a predetermined gap therebetween; an electro-opticmaterial held in the gap; an opposed electrode formed on one of thesubstrates; and a semiconductor thin film which can provide pixelelectrodes formed on the other substrate and thin film transistors whichdrive the pixel electrodes, wherein the semiconductor thin film is asemiconductor film crystallized by irradiating the polycrystalsemiconductor film or the amorphous semiconductor film with light beamshaving a predetermined light intensity distribution through a phasemodulation element in which a phase of outgoing light beams relative toincident light beams varies depending on each position and an imageformation optical system.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a schematic view illustrating an example of a structure of acrystallization apparatus according to an embodiment of the presentinvention;

FIG. 2 is a schematic view illustrating an example of an internalstructure of an illumination system depicted in FIG. 1;

FIGS. 3A to 3F are schematic views illustrating a basic principle of thepresent invention;

FIGS. 4A to 4C are schematic views illustrating a relationship betweenchanges in phase and a light intensity in a point spread distributionrange;

FIGS. 5A and 5B are schematic views illustrating a relationship betweena pupil function and a point spread function in an image formationoptical system;

FIG. 6A is a schematic view illustrating an example of an embodiment ofa phase modulation element;

FIG. 6B is a schematic view illustrating an example of changes in areashares of each cell of the phase modulation element depicted in FIG. 6A;

FIG. 7 is a schematic view illustrating another embodiment of the phasemodulation element according to the present invention;

FIG. 8 is a schematic view illustrating still another embodiment of thephase modulation element according to the present invention;

FIG. 9A is a schematic view illustrating yet another embodiment of thephase modulation element according to the present invention;

FIG. 9B is a schematic view showing a light intensity distributionprovided by the phase modulation element depicted in FIG. 9A;

FIG. 9C is a schematic view illustrating an example that the phasemodulation element depicted in FIG. 9A is also arranged in a directionindicated by an arrow y orthogonal to a direction indicated by an arrowx;

FIG. 9D is a schematic view showing a light intensity distributionprovided by the phase modulation element illustrated in FIG. 9C;

FIG. 10A is a schematic view illustrating a further embodiment of thephase modulation element according to the present invention;

FIG. 10B is a schematic view showing a light intensity distributionprovided by the phase modulation element depicted in FIG. 10A;

FIG. 11A is a schematic view illustrating a still further embodiment ofthe phase modulation element according to the present invention;

FIG. 11B is a schematic view showing a light intensity distributionprovided by the phase modulation element depicted in FIG. 11A;

FIG. 12A is a schematic view illustrating a yet further embodiment ofthe phase modulation element according to the present invention;

FIG. 12B is a schematic view showing a light intensity distributionalong a line A-A in FIG. 12A;

FIG. 12C is a schematic view showing a light intensity distributionalong a border line B-B in FIG. 12A;

FIG. 13 is a schematic view illustrating characteristics of the phasemodulation element depicted in FIGS. 12A to 12C;

FIG. 14A is a schematic view illustrating another embodiment of thephase modulation element according to the present invention;

FIG. 14B is a schematic view illustrating a modification of the phasemodulation element depicted in FIG. 14A;

FIG. 15A is a schematic view showing in a contour map a light intensitydistribution obtained in the phase modulation element depicted in FIG.14A;

FIG. 15B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 15A;

FIG. 15C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 15A;

FIG. 16A is a schematic view illustrating still another embodiment ofthe phase modulation element according to the present invention;

FIG. 16B is a schematic view illustrating a modification of the phasemodulation element depicted in FIG. 16A;

FIG. 17A is a schematic view showing in a contour map a light intensitydistribution obtained in the phase modulation element depicted in FIG.16A;

FIG. 17B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 17A;

FIG. 17C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 17A;

FIG. 18A is a schematic view illustrating yet another embodiment of thephase modulation element according to the present invention;

FIG. 18B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 18A;

FIG. 18C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 18A;

FIG. 19A is a schematic view illustrating a further embodiment of thephase modulation element according to the present invention;

FIG. 19B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 19A;

FIG. 19C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 19A;

FIG. 20A is a schematic view showing in a contour map a light intensitydistribution obtained in the phase modulation element depicted in FIG.19A;

FIG. 20B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 20A;

FIG. 20C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 20A;

FIG. 21A is a schematic view illustrating a still further embodiment ofthe phase modulation element according to the present invention;

FIG. 21B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 21A;

FIG. 21C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 21A;

FIG. 22A is a schematic view illustrating a yet further embodiment ofthe phase modulation element according to the present invention;

FIG. 22B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 22A;

FIG. 22C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 22A;

FIG. 23A is a schematic view illustrating another embodiment of thephase modulation element according to the present invention;

FIG. 23B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 23A;

FIG. 23C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 23A;

FIG. 24A is a schematic view illustrating still another embodiment ofthe phase modulation element according to the present invention;

FIG. 24B is a schematic view showing a light intensity distributionalong the line A-A in FIG. 24A;

FIG. 24C is a schematic view showing a light intensity distributionalong the border line B-B in FIG. 24A;

FIG. 25A is a schematic view illustrating yet another embodiment of thephase modulation element according to the present invention;

FIG. 25B is a schematic view showing a light intensity distributionalong the lien A-A in FIG. 25A;

FIG. 25C is a schematic view showing a light intensity distributionalong the line the border line B-B in FIG. 25A;

FIGS. 26A to 26E are schematic view illustrating an example of a processto manufacture an electronic device on a transparent substrate obtainedby a crystallization apparatus according to the present invention;

FIG. 27 is a schematic view illustrating an example to apply atransparent substrate obtained by the crystallization apparatusaccording to the present invention to a display apparatus, e.g., anactive matrix type liquid crystal display; and

FIG. 28 is a schematic view illustrating an example to apply atransparent substrate obtained by the crystallization apparatusaccording to the present invention to a display apparatus, e.g., anactive matrix type liquid crystal display.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments according to the present invention will now be describedhereinafter with reference to the accompanying drawings.

FIG. 1 is a view schematically showing a structure of a crystallizationapparatus according to an embodiment of the present invention. Further,FIG. 2 is a view schematically showing an internal structure of anillumination system of FIG. 1. Referring to FIGS. 1 and 2, acrystallization apparatus according to this embodiment comprises anillumination system 2 used to illuminate a phase modulation element 1. Astructure and an effect of the phase modulation element 1 will bedescribed later.

The illumination system 2 comprises a laser beam source which generatesincident light beams which enter the phase modulation element 1, e.g., aKrF excimer laser beam source 2 a which supplies light beams having awavelength of 248 nm used to crystallize a non-single crystalsemiconductor film such as an amorphous silicon film or a polycrystalsilicon film. It is to be noted that any other appropriate beam sourcesuch as an XeCl excimer laser beam source or a YAG laser beam source canbe also used as the beam source 2 a.

Laser beams supplied from the beam source 2 a are expanded through abeam expander 2 b and then enter a first fly-eye lens 2 c.

A plurality of pseudo-beam sources are formed on a rear focal plane ofthe first fly-eye lens 2 c (an image of the beam source 2 a istransferred to the rear focal plane of the first fly-eye lens 2 c andpseudo-beam sources are defined). Light fluxes from the rear focal planeof the first fly-eye lens 2 c, i.e., the plurality of (pseudo-) beamsources are led to an incident plane of a second fly-eye lens 2 ethrough a first condenser optical system 2 d. As a result, morepseudo-beam sources than those on the rear focal plane of the firstfly-eye lens 2 c are formed on a rear focal plane of the second fly-eyelens 2 e (an image of the first fly-eye lens 2 c is transferred on therear focal plane of the second fly-eye lens 2 e and pseudo-beam sourcesare defined). Light fluxes from the plurality of beam sources formed onthe rear focal plane of second fly eye lens 2 e are caused to enter thephase modulation element 1 through a second condenser optical system 2f.

The first fly-eye lens 2 c and the first condenser optical system 2 dconstitute a first homogenizer (i.e., a homogenization mechanism) whichgives homogenization (effect) to illumination beams from the beam source2 a. Therefore, the laser beams supplied from the beam source 2 a arecaused to enter the second fly-eye lens 2 e in a state that an in-planeintensity distribution is homogenized by this first homogenizer.

Furthermore, the second fly-eye lens 2 e and the second condenseroptical system 2 f constitute a second homogenizer, and the phasemodulation element 1 is irradiated with laser beams whose incident angleis homogenized by the first homogenizer in a state that the in-planeintensity distribution is substantially homogeneous. In this manner, anentire area of the phase modulation element 1 is irradiated with thelaser beams having the homogenous incident angle distribution and thehomogenous in-plane intensity distribution by the first fly-eye lens 2c, the first condenser optical system 2 d, the second fly-eye lens 2 eand the second condenser optical system 2 f.

The laser beams phase-modulated by the phase modulation element 1 arecaused to enter a processed substrate 4 provided on an outgoingradiation side of an image formation optical system 3.

The image formation optical system 3 comprises a convex lens 3 a, aconvex lens 3 b and an aperture diaphragm 3 c provided between the bothlenses, and can position the phase modulation element 1 and theprocessed substrate 4 in an optically conjugate positional relationship.

In other words, the processed substrate 4 has a film which is subjectedto crystallization processing, and is set on a surface opticallyconjugate with the phase modulation element 1 (image surface of theimage formation optical system 3). It is to be noted that the processedsubstrate 4 is positioned and held at a predetermined position on asubstrate stage 5 by using a vacuum chuck, an electrostatic chuck or thelike.

The aperture diaphragm 3 c can arbitrary set a size of an aperture(light transmission portion). It is to be noted that the aperturediaphragm 3 c can be arbitrarily selected from, e.g., an iris diaphragmwhich can continuously change a size of the aperture. Moreover, aplurality of plate-like bodies each of which has an aperture with apredetermined size provided thereto may be prepared and arbitrarily setin a light path. In any case, the size of the aperture of the aperturediaphragm 3 c (which is substantially an image side numerical apertureNA of the image formation optical system 3) is set so as to generate anecessary light intensity distribution on a semiconductor film of theprocessed substrate 4 as will be described later.

It is to be noted that the image formation optical system 3 may be arefraction type optical system, a reflection type optical system or arefraction/reflection type optical system. Additionally, the processedsubstrate 4 is obtained by sequentially forming an underlying film(lower layer protection film) and a non-single crystal semiconductorfilm such as an amorphous silicon film on, e.g., a liquid crystaldisplay glass sheet by chemical vapor deposition (CVD).

FIGS. 3A to 3F are views illustrating a basic principle of the presentinvention. Like reference numerals denote parts equal to those in FIGS.1 and 2, thereby eliminating their detailed explanation.

Generally, a light amplitude distribution U (x, y) of image formation bythe phase modulation element 1 is represented by the followingexpression (1):

U(x,y)=T(x,y)*ASF(x,y)  (1)

It is to be noted that T (x, y) indicates a complex amplitudetransmittance distribution of the phase modulation element 1; *, aconvolution (convolution integral); an ASF (x, y), a point spreadfunction of the image formation optical system 3. Furthermore, the pointspread function is defined as an amplitude distribution of a point imageobtained by the image formation optical system.

It is to be noted that the complex amplitude transmittance distributionT of the phase modulation element 1 is represented by the followingexpression (2) since it has a homogenous amplitude;

T=T ₀ e ^(iφ)(x,y)  (2)

It is to be noted that T₀ is a fixed value and φ (x, y) indicates aphase distribution in the expression (2).

Moreover, when the image formation optical system 3 has a homogenouscircular pupil and no aberration, a relationship represented by thefollowing expression (3) is achieved in connection with the point spreadfunction ASF (x, y):

ASF(x,y)∝2J ₁(2π/λ·NA·r)/(2π/λ·NA·r)  (3)

where r=(x²+y²)^(1/2)

It is to be noted that J₁ indicates a Bessel function, λ indicates awavelength of light beams and NA indicates an image side numeralaperture of the image formation optical system 3 as describe above inthe expression (3).

The point spread function of the image formation optical system 3depicted in FIG. 3A is a light intensity distribution on an imagesurface 3 f of the processed substrate 4 and shown in FIG. 3B. Ahorizontal axis shows an incident plane of the processed substrate 4,and a vertical axis shows an incident light intensity. The point spreadfunction of the image formation optical system 3 depicted in FIG. 3A canbe approximated by using a cylindrical shape 3 e having a diameter Rindicated by a broken line in FIG. 3B. That is, a result of integratingthe complex amplitude distribution in a circle having a diameter R′(value optically corresponding to the diameter R in FIG. 3B) on thephase modulation element 1 depicted in FIG. 3C determines a complexamplitude on the image surface 3 f shown in FIG. 3A.

As described above, the light amplitude of image formation image-formedon the image plane 3 f, i.e., the light intensity is given by theconvolution between the complex amplitude transmittance distribution ofthe phase modulation element 1 and the point spread function.

Giving a consideration by approximating the point spread function byusing the cylindrical shape 3 e, a result obtained by integrating thecomplex amplitude transmittance of the phase modulation element 1 with ahomogenous weight in the circular point spread distribution range shownin FIG. 3C becomes the complex amplitude on the image surface 3 f, and asquare of its absolute value becomes the light intensity. It is to benoted that the point spread distribution range R in the image formationoptical system 3 means a range in an intersection 3 j of an amplitudecurve and a horizontal axis 3 i in FIG. 3B plotted by using the pointspread function.

Therefore, the light intensity is increased as a change in phase in thepoint spread distribution range R is small. On the contrary, the lightintensity is decreased as a change in phase is large. This point can bereadily understood by considering a sum of phase vectors 3 h in a unitcircle 3 g as shown in FIG. 3D. When the image surface 3 f is an object,e.g., a semiconductor film, the point spread function of FIG. 3B is apoint spread function such as shown in FIG. 3F. FIG. 3E is a viewshowing a point on the image surface 3 f, and a light intensity at thispoint is determined by the above-described process.

FIGS. 4A to 4C are views showing a typical relationship between changesin phase in the point spread distribution range R and the lightintensity. FIG. 4A is a view showing a case that phase values in fourareas are all zero degree, a sum of four phase vectors 4 g each havingan amplitude of E in a direction of zero degree is an amplitude 4E, andits square corresponds to a light intensity 16I.

FIG. 4B is a view showing a case that phase values of two areas are zerodegree and phase values of the other two areas are 90 degrees. In thiscase, a sum of the two phase vectors in the direction of zero degree andthe two phase vectors in the direction of 90 degrees corresponds to anamplitude 2√2E, and its square corresponds to a light intensity 8I. FIG.4C is a view showing a case of an area having a phase value of zerodegree, an area having a phase value of 90 degrees, an area having aphase value of 180 degrees and an area having a phase value of 270degrees. In this case, an amplitude of a sum of a phase vector 4 s inthe direction of zero degree, a phase vector 4 t in the direction of 90degrees, a phase vector 4 u in the direction of 180 degrees and a phasevector 4 v in the direction of 270 degrees is OE, and its squarecorresponds to a light intensity OI.

FIGS. 5A and 5B are views showing a relationship between a pupilfunction and the point spread function in the image formation opticalsystem 3.

Generally, a point spread function (FIG. 5B) is given by a Fouriertransform of a pupil function (FIG. 5A). Specifically, when the imageformation optical system 3 has a homogenous circular pupil and noaberration, the point spread function ASF (x, y) is presented by theabove-described expression (3). However, it is not restricted to theabove if there is an aberration in the image formation optical system 3or the image formation optical system 3 has a pupil function other thanthe homogenous circular pupil.

When the image formation optical system 3 has the homogenous circularpupil and no aberration, it is known that the a radius R/2 of a centralarea (i.e., an airy disk) until the point spread function becomes 0first is represented by the following expression (4):

R/2=0.61λ/NA  (4)

In the present invention, the point spread distribution range R means acircular central area until the point spread function F(x) becomes zerofirst as shown in FIGS. 3B and 5B. As apparent from FIGS. 4A to 4C, whena circle optically corresponding to the point spread distribution rangeR of the image formation optical system includes a plurality of (four inFIGS. 4A to 4C) phase modulation units, an amplitude of the light beams,i.e., the light intensity can be analytically controlled in accordancewith a simple calculation by using a sum of a plurality of phase vectors4 g. As a result, a relatively complex light intensity distribution canbe comparatively readily obtained.

Therefore, in the present invention, in order to freely control thelight intensity, the phase modulation unit of the phase modulationelement 1 must be optically smaller than a radius of the point spreaddistribution range R (see FIG. 3B) of the image formation optical system3, i.e., R/2. In other words, a size of a phase distribution based onthe phase modulation unit of the phase modulation element 1 must besmaller than the radius R/2 of the point spread distribution range R ofthe image formation optical system 3 when converted to the imageformation surface of the image formation optical system on the imageside of the image formation optical system 3. Here, in case of alater-described cell type, the phase modulation unit means a size of ashortest side of the cell. In case of a pixel type, it means a length ofone side.

A description will now be given as to an embodiment of the phasemodulation element 1 which can be used in this embodiment.

FIG. 6A schematically shows a structure of the phase modulation element1, and FIG. 6B shows changes in area shares of each cell of the phasemodulation element depicted in FIG. 6A.

Referring to FIG. 6A, the phase modulation element 1 has a plurality ofcells 21 which have sizes optically smaller than the radius R/2 of thepoint spread distribution range R of the image formation optical system3 and are indicated by a rectangular wavy line. Further, each phasemodulation element 1 has a first area 21 a which is shaded and has afirst phase value φ1 and a second area 21 b which is shown as anon-shaded space and has a second phase value φ2.

As shown in FIG. 6A, area shares of the first area 21 a having the phasevalue φ1 (e.g., 90 degrees) and the second area 21 b having the phasevalue φ2 (e.g., zero degree) in each cell 21 vary in accordance witheach cell. In other words, there is provided a phase distribution thatthe area shares of the first area 21 a having the phase value φ1 and thesecond area 21 b having the phase value φ2 vary depending on eachposition. More specifically, an occupied area of the second area 21 bhaving the phase value φ2 in the cell is largest in the cell shown onthe leftmost side, and it is smallest in the cell shown on the rightmostside. It monotonously varies between these cells. Therefore, in thephase modulation element 1 formed of six cells depicted in FIG. 6, sizesof the areas having the different phase values continuously vary in eachcell as shown in FIG. 6B. The light beams to enter the phase modulationelement 1 are transmitted from a front surface of a paper sheet (frontside) in the direction of a rear surface of the same (inner side) asindicated by an arrow z.

As described above, the phase modulation element 1 has a phasedistribution based on the phase modulation unit (cell) 21 having anoptically smaller size than the radius R/2 of the point spreaddistribution range R of the image formation optical system 3. Therefore,by appropriately changing the area shares of the first area 21 a and thesecond area 21 b in each phase modulation unit 21, i.e., a sum of thetwo phase vectors, the light intensity distribution formed on theprocessed substrate 4 (see FIG. 1) can be controlled by using apredetermined calculation. The phase modulation element 1 having thefirst and second phase values φ1 and φ2 can be manufactured by selectinga thickness of, e.g., a quarts glass so as to form the first and secondphase values φ1 and φ2. A change in thickness of the quartz glass can beformed by selective etching or an FIB (Focused Ion Beam).

FIG. 7 is a view schematically showing another embodiment of the phasemodulation element 1.

Referring to FIG. 7, the phase modulation element 1 has a plurality ofrectangular pixels 22 each of which is optically smaller than the radiusR/2 of the point spread distribution range R of the image formationoptical system 3. The plurality of pixels 22 are closely arranged in theboth vertical and horizontal directions, and each pixel 22 has a fixedphase value. Specifically, the phase modulation element 1 has shadedfirst pixels 22 a each having a first phase value φ1 (e.g., 90 degrees)and non-shaded second pixels each of which is shown as a space and has asecond phase value φ2 (e.g., zero degree). The incident light beams onthe phase modulation element 1 are transmitted from a front surface of apaper sheet (front side) in a rear surface direction (inner side) asindicated by an arrow z.

As shown in FIG. 7, the number of pixels having the same phase value perunit range (indicated by a circle C of a broken line) opticallycorresponding to the point spread distribution range R (see FIG. 3B) ofthe image formation optical system 3 is changed in accordance with eachunit range. In other words, the phase modulation element 1 shown in FIG.7 has a phase distribution that the area shares of each first pixel 22 aas a first area having the phase value φ1 and each second pixel 22 b asa second area having the phase value φ2 vary depending on each positionlike the phase modulation element shown in FIG. 6A.

As described above, the phase modulation element 1 shown in FIG. 7 has aphase distribution based on the phase modulation unit (pixel) 22 havinga size optically smaller than the radius R/2 of the point spreaddistribution range R of the image formation optical system 3. Therefore,by appropriately changing the area shares of the first pixels 22 a andthe second pixels 22 b in a unit range C in the phase modulation element1 optically corresponding to the point spread distribution range R ofthe image formation optical system 3, i.e., a sum of phase vectors, alight intensity distribution formed on the processed substrate 4 can becontrolled by using a predetermined calculation.

FIG. 8 is a view schematically showing still another embodiment of thephase modulation element 1. Referring to FIG. 8, the phase modulationelement 1 has a plurality of stripe-like areas 23 defined by elongatedtriangle shapes each having an optically smaller width than a radius ofthe unit range C corresponding to the point spread distribution range Rof the image formation optical system 3. The plurality of stripe-likeareas 23 are closely arranged as shown in the drawing, and eachstripe-like area 23 has a fixed phase value.

Specifically, the phase modulation element 1 has each shaded firststripe-like area 23 a having a first phase value φ1 (e.g., 90 degrees)and each non-shaded second stripe-like area 23 b which is shown as aspace and has a second phase value φ2 (e.g., zero degree).

As shown in FIG. 8, a width of each stripe-like area 23 a or 23 b variesalong the longitudinal direction (indicated by an arrow x). In otherwords, there is a phase distribution that area shares of the firststripe-like area 23 a as a first area having the phase value φ1 and thesecond stripe-like area 23 b as a second area having the phase value φ2vary depending on each position.

The incident light beams on the phase modulation element 1 aretransmitted from a front surface of a paper sheet (front side) in adirection of a rear surface (inner side) of the same in FIG. 8 asindicated by an arrow z. This phase modulation element 1 can bemanufactured by selecting a thickness of, e.g., a quartz glass so as toform the first and second phase values φ1 and φ2. A change in thicknessof the quartz glass can be formed by selective etching or an FIB.

As described above, the phase modulation element 1 shown in FIG. 8 hasthe phase distribution based on the phase modulation unit (stripe-likearea) having an optically smaller width than the radius R/2 of the pointspread distribution range R of the image formation optical system 3.Therefore, by appropriately changing the area shares of the firststripe-like area 23 a and the second stripe-like area 23 b in a unitrange C optically corresponding to the point spread distribution range Rof the image formation optical system 3, i.e., a sum of a plurality ofphase vectors, a light intensity distribution formed on the processedsubstrate 4 can be controlled by using a predetermined calculation.

FIG. 9A is a view schematically showing yet another embodiment of thephase modulation element 1. Referring to FIG. 9A, the phase modulationelement 1 has a line-and-space pattern 24 having an optically smallerwidth than a radius of the point spread distribution range R (see FIGS.3B and 7, which is indicated by “C” in FIG. 9A) of the image formationoptical system 3. Incidentally, when this pattern is simply referred toas the line-and-space pattern, it generally means a set of atransmission area and a non-transmission area. However, in the presentinvention, it is notated as the line and space with respect to arepetition of two different types of phases.

In FIG. 9A, each shaded line portion 24 a has a first phase value φ1(e.g., 90 degrees), and each non-shaded space portion 24 b shown as aspace has a second phase value φ2 (e.g., zero degree). When a pitch isindicated with a ratio of a width of the line portion 24 a and a widthof the space portion 24 b which are adjacent to each other, i.e., a partcorresponding to the first phase value φ1 and a part corresponding tothe second phase value φ2 being regarded as a set, a percentage of thefirst phase value φ1 in each pitch varies along a direction indicated byan arrow x.

Specifically, a duty ratio (width of the line portion 24 a/pitch) is 0%at the center of the line-and-space pattern 24, the duty ratio islinearly increased in increments of 5% toward a periphery, and the dutyratio is 50% on the both sides. As described above, the phase modulationelement shown in FIG. 9A has a phase distribution that area shares ofthe line portion 24 a as a first area having the phase value φ1 and thespace portion 24 b as a second area having the phase value φ2 varydepending on each position like the embodiment of the phase modulationelement described above.

As mentioned above, the phase modulation element 1 shown in FIG. 9A hasthe phase distribution based on a phase modulation unit (the lineportion or the space portion) C having an optically smaller width thanthe radius R/2 of the point spread distribution range R of the imageformation optical system 3. Therefore, by appropriately changing thearea shares of the line portion 24 a and the space portion 24 b in theunit range C optically corresponding to the point spread distributionrange R of the image formation optical system 3, i.e., a sum of aplurality of phase vectors, a light intensity distribution formed on theprocessed substrate 4 (see FIG. 1) can be controlled by using apredetermined calculation.

Specifically, as shown in FIG. 9A, a part in the vicinity of the centerin the longitudinal (arrow x) direction is determined to substantiallyhave the second phase value φ2, and the line-and-space pattern 24 isformed in such a manner that a ratio of the area having the first phasevalue φ1 is gradually increased toward the both end portions in adirection indicated by the arrow x. In this case, the incident lightbeams which are transmitted from a front surface (front side) of a papersheet in a direction of a rear surface (inner side) of the same asindicated by an arrow z demonstrate a light intensity distribution witha convex pattern that a light intensity becomes largest at the centralposition corresponding to the center of the line-and-space pattern 24and the light intensity becomes smallest at positions on both sidescorresponding to the both sides of the line-and-space pattern 24 asshown in FIG. 9B.

Actually, since the line-and-space pattern 24 is repeatedly formed alongthe both sides in the direction indicated by the arrow, there isobtained a light intensity distribution with a concave pattern that thelight intensity is minimum at the center and the light intensity isone-dimensionally and substantially linearly increased toward theperiphery, i.e., a light intensity distribution with a V-shaped (analphabetical letter [V] and an inverted [V] are alternately arranged inzigzags) pattern. This phase modulation element 1 can be manufactured byselecting a thickness of, e.g., a quartz glass so as to form the firstand second phase values φ1 and φ2. A change in thickness of the quartzglass can be formed by selective etching or an FIB. Incidentally, inorder to obtain an accurately linear light intensity distribution suchas shown in FIG. 9B, it is desirable for the areas 24 a and 24 b havingthe different phase values to use a duty ratio (width of the lineportion 24 a/pitch) which is obtained in accordance with the expression(1) and non-linearly increased (e.g., six steps of 0%, 5%, 11%, 18%, 28%and 50%) in place of using a duty ratio which is linearly increased asdescribed above.

Meanwhile, when the processed substrate 4 is irradiated with laser beamshaving a light intensity with such a concave pattern as shown in FIG.9B, there is known a fact that a crystal nucleus is generated at aposition on the processed substrate 4 substantially corresponding to abottom portion (part where the light intensity is minimum) of the lightintensity distribution. That is, a growth of a crystal (increase inparticle size) which is a change from an amorphia to a crystal advancesalong a temperature gradient from the crystal nucleus toward theperiphery. At a part where the light intensity of the laser beams withwhich the processed substrate 4 is irradiated is not more than athreshold value α, the semiconductor film (Si) is not fused (remains asan amorphous material), or a surface thereof is partially fused and thesemiconductor film remains in a silicon state (no crystal growth), andthe crystal growth starts when the threshold value α is exceeded.

Therefore, in order to obtain a crystal with a large particle size whichis as large as possible by adopting the light intensity distributionwith the concave pattern, it is desirable that a value of the lightintensity at the bottom of the light intensity distribution with theconcave pattern is slightly lower than this value α. In other words, itis desirable that the value α used to obtain the crystal with a largeparticle size has the light intensity slightly larger than a bottomvalue of the light intensity distribution with the concave pattern. Thatis, the crystal is caused to grow in the lateral direction from thecrystal nucleus by using the phase modulation element 1 shown in FIG. 9Ato minimize the light intensity at a preset arbitrary position (form abottom portion of the light intensity distribution) as shown in FIG. 9Band using the light intensity distribution with a pattern whichincreases the light intensity from the bottom portion toward theperiphery in the light intensity distribution, thereby generating acrystallized semiconductor film with a large particle size.

In particular, since the temperature gradient toward the periphery alsobecomes linear in the light intensity distribution with a V-shapedpattern that the light intensity is linearly increased toward theperiphery among the concave patterns, the growth of the crystal does notstop, and a crystallized semiconductor film with a larger particle sizecan be generated. Furthermore, since an additional irregular lightintensity distribution is not produced as different from the prior artusing the phase shifter as shown in FIG. 9B, crystal grains can begenerated in an array form with a high filling ratio by using the lightintensity distribution with the above-described pattern.

It is to be noted that the light intensity distribution 24 d having aconcave pattern similar to the V-shaped pattern shown in FIG. 9B is notrestricted to one axial direction and can be provided in an arbitrarydirection by repeating the phase distribution shown in FIGS. 6A, 7 and 8along a predetermined direction (direction along which area sharesvary). As a result, causing the lateral growth of the crystal from thecrystal nucleus based on the light intensity distribution 24 d havingthe same concave pattern as that shown in FIG. 9B can likewise generatea crystallized semiconductor film with a large particle size by usingthe phase modulation element depicted in FIGS. 6A, 7 and 8.

As shown in FIG. 9C, it is to be noted that such a light intensitydistribution to which an irregular distribution is given in a planedirection as shown in FIG. 9C can be obtained by offsetting a positionof the phase value φ2 by a predetermined quantity in a directionindicated by an arrow y orthogonal to a direction indicated by an arrowx in order to provide a matrix form to the phase modulation elementshown in FIG. 9A. Moreover, in such a matrix type phase modulationelement as shown in FIG. 9C, a size of one side of a phase modulationelement block as a unit is, e.g., 10 μm in the direction indicated bythe arrow x and 5 μm in the direction indicated by the arrow y.

FIG. 10A is a view schematically showing a further structure of thephase modulation element according to the present invention. Referringto FIG. 10A, the phase modulation element 1 has a plurality ofrectangular pixels 25 each of which is optically smaller than the radiusR/2 of the point spread distribution range R (i.e., a unit range C) ofthe image formation optical system 3. The plurality of pixels 25 areclosely arranged in the both vertical and horizontal direction, eachpixel 25 has a fixed phase value, and the phase value varies inaccordance with each pixel 25. In other words, the phase modulationelement 1 shown in FIG. 10A has a cyclic divided area structure, eachdivided area (pixel) 25 has a fixed phase value, and the phasemodulation element 1 has a phase distribution that the phase valuevaries in accordance with each divided area.

Specifically, the phase modulation element 1 has a first pixel 25 a witha first phase value φ1 (e.g., 90 degrees), a second pixel 25 b with asecond phase value φ2 (e.g., 67.5 degrees), a third pixel 25 c with athird phase value φ3 (e.g., 45 degrees), a fourth pixel 25 d with afourth phase value φ4 (e.g., 22.5 degrees), and a fifth pixel 25 e witha fifth phase value φ5 (e.g., zero degree). Additionally, pixels otherthan the first to fifth pixels 25 a to 25 e have the same phase value(e.g., zero degree). That is, in the phase modulation element 1 shown inFIG. 10A, a change quantity of the phase value is small in an area onthe fifth pixel 25 e side having the fifth phase value φ5 given thereto,a change quantity of the phase value is large in an area on the firstpixel 25 a side having the first phase value φ1 given thereto, and achange quantity of the phase value monotonously varies between theseareas. Therefore, as indicated by an arrow z, a light intensity of thelight beams transmitted through the phase modulation element 1 from afront surface (front side) of a paper sheet in a direction of a rearsurface (inner side) of the same is larger on the fifth pixel 25 e sidethan the first pixel 25 a side as shown in FIG. 10B.

As described above, the phase modulation element 1 has a phasedistribution based on a phase modulation unit (pixel) 25 having anoptically smaller size than the radius R/2 of the point spreaddistribution range R (unit range C) of the image formation opticalsystem 3. Further, by appropriately changing the distribution of thephase values, i.e., a sum of a plurality of phase vectors, a lightintensity distribution formed on the processed substrate 4 can becontrolled by using a predetermined distribution. This phase modulationelement 1 can be manufactured by selecting a thickness of, e.g., aquartz glass so as to form a desired phase value distribution. A changein thickness of the quartz glass can be formed by selective etching oran FIB.

It is to be noted that repeating the phase distribution shown in FIG.10A in a direction along which the phase value varies can provide alight intensity distribution similar to the V-shaped (an alphabeticalletter [V] and an inverted [V] are alternately arranged in zigzags)pattern shown in FIG. 9B. As a result, the sufficient lateral growth ofthe crystal from a crystal nucleus can be realized based on the lightintensity distribution with the concave pattern, thereby generating acrystallized semiconductor film with a large particle size.

FIG. 11A is a view schematically showing a still further structure ofthe phase modulation element according to the present invention.Referring to FIG. 11A, the phase modulation element 1 has aline-and-space pattern 26 having an optically smaller width than theradius R/2 of the point spread distribution range R (unit range C) ofthe image formation optical system 3. Here, a duty ratio (width of aline portion/pitch) is 50% and fixed over the entire line-and-spacepattern 26. However, a phase value of each shaded line portion varies inaccordance with each line portion.

That is, a phase value φ1 of the line portion 26 a is closest to a phaseof the space portion at the center of the line-and-space pattern 26, aphase value φ11 of each line portion 26 k on the both sides is farthestfrom the phase of the space portion, and the phase value of the lineportion monotonously varies between these values. The phase value ineach space portion of the line-and-space pattern 26 is fixed.Specifically, a phase value φ1 of a line portion 26 a is zero degree, aphase value φ2 of a line portion 26 b is 25.9 degrees, a phase value φ3of a line portion 26 c is 36.9 degrees, a phase value φ4 of a lineportion 26 d is 45.6 degrees, a phase value φ5 of a line portion 26 e is53.2 degrees, and a phase value φ6 of a line portion 26 f is 60.0degrees.

Furthermore, a phase value φ7 of a line portion 26 g is 66.5 degrees, aphase value φ8 of a line portion 26 h is 72.6 degrees, a phase value φ9of a line portion 26 i is 78.5 degrees, a phase value φ10 of a lineportion 26 j is 84.3 degrees, and a phase value φ11 of a line portion 26k is 90.0 degrees. On the other hand, phase values of the respectivespace portions are all zero degree. In this manner, the phase modulationelement 1 has a cyclic divided area structure, each divided area (theline portion or the space portion) has a fixed phase value, and thephase modulation element 1 has a phase distribution that the phase valuevaries in accordance with each divided area.

As described above, the phase modulation element 1 has a phasedistribution based on a phase modulation unit (the line portion or thespace portion) having an optically smaller width than the radius R/2 ofthe point spread distribution range R of the image formation opticalsystem 3. Therefore, by appropriately changing a distribution of thephase values of the line portions in an optically smaller unit rangethan the point spread distribution range R of the image formationoptical system 3, i.e., a sum of a plurality of phase vectors, a lightintensity distribution formed on the processed substrate 4 (see FIG. 4)can be controlled by using a predetermined calculation. The incidentlight beams onto the phase modulation element 1 are transmitted from afront surface (front side) of a paper sheet in a direction of a rearsurface (inner side) of the same as indicated by an arrow z in FIG. 11A.This phase modulation element 1 can be readily manufactured by selectinga thickness of, e.g., a quartz glass so as to form a desired phase valuedistribution. A change in thickness of the quartz glass can be formed byselective etching or an FIB.

Further, repeating the phase distribution shown in FIG. 11A along apredetermined direction (direction along which the phase value varies)can obtain a light intensity distribution with a concave pattern shownin FIG. 11B which is similar to the V-shaped pattern depicted in FIG.9B, thereby forming crystal grains in an array form. As a result, thesufficient lateral growth from a crystal nucleus of a crystal can berealized based on the light intensity distribution with the concavepattern shown in FIG. 11A, thus generating a crystallized semiconductorfilm with a large particle size.

FIG. 12A is a schematic view illustrating a yet further embodiment ofthe phase modulation element according to the present invention.Referring to FIG. 12A, the phase modulation element 1 has a firststripe-like area 31 which has a first phase distribution and extendsalong a direction indicated by an arrow x which is a direction alongwhich a phase varies, and a second stripe-like area 32 which has asecond phase distribution and extends along the direction indicated bythe arrow x in substantially parallel with the first stripe-like area 31which is the direction along the phase varies. The first stripe-likearea 31 an the second stripe-like area 32 are adjacent to each otherwith a border line 33 in the phase change direction therebetween, and anaverage phase value on the first stripe-like area 31 side issubstantially different from an average phase value on the secondstripe-like area 32 side in a local area on the border line 33. It is tobe noted that light intensity characteristics having a linear fallinggradient in directions indicated by arrows 31 x and 32 x in FIG. 12A canbe obtained based on, e.g., the phase distribution shown in FIG. 11A.

The first stripe-like area 31 and the second stripe-like area 32 areconfigured to have substantially the same light intensity distributionswhich are formed in accordance therewith. In a first local area 34 onthe border line 33 corresponding to a part where the light intensity ofthe light intensity distribution is small, an average phase value on thefirst stripe-like area 31 side is substantially different from anaverage phase value on the second stripe-like area 32 side. On the otherhand, in a second local area 35 on the border line 33 corresponding to apart where the light intensity of the light intensity distribution islarge, an average phase value φave on the first stripe-like area 31 sideis substantially equal to an average phase value save on the secondstripe-like area 32 side. The average phase value φave is represented bythe following expression:

φave=∫_(D)φ(x.y)dxdy

D is an integration range, and it is, e.g., a range close to the centerpartitioned by the border line 33 in the point spread distribution rangeR. e(x, y) is a unit vector having a phase at coordinates (x, y), andarg is a function used for obtaining the phase from the vector.

The light beams transmitted through the phase distribution pattern shownin FIG. 12A demonstrate a light intensity distribution 120 with aconcave pattern having, e.g., a V-shaped (an alphabetical letter [V] andan inverted [V] are alternately arranged in zigzags) conformation alongthe phase change direction in each of the first stripe-like area 31 andthe second stripe-like area 32 sufficiently distanced from the borderline 33 as shown in FIG. 12B.

A light intensity distribution along the border line 33 shown in FIG.12C produces a drop 121 in a light intensity with an inverse peakpattern corresponding to a part where the light intensity is small in anarea corresponding to the first local area 34 as described above inconnection with FIGS. 3B to 3F since the average phase value on thefirst stripe-like area 31 side is substantially different from theaverage phase value on the second stripe-like area 32 side in the firstlocal area 34 on the border line 33.

However, since the average phase value on the first stripe-like area 31side is substantially equal to the average phase value on the secondstripe-like area 32 side in the second local area 35 on the border line33, the affect by the second local area 35 is rarely produced in a partwhere the light intensity is large.

In the phase modulation element having the phase pattern shown in FIG.12A, there is obtained a combined light intensity distribution of thelight intensity distribution 120 with the concave pattern having, e.g.,the V-shaped (an alphabetical letter [V] and an inverted [V] arealternately arranged in zigzags) conformation and the light intensitydistribution with the inverse peak pattern 121 including a part wherethe light intensity is locally small in this light intensitydistribution 120 with the concave pattern, i.e., a light intensitydistribution with the concave pattern 120 and the inverse peak patternlocally including a part where the light intensity is locally small.

In the light intensity distribution with the concave pattern and theinverse peak pattern including the part where the light intensity islocally small, it is desirable to set the value α described withreference to FIG. 9B so as to be positioned in the vicinity of theborder between the light intensity distribution 121 with the inversepeak pattern and the light intensity distribution 120 with the concavepattern or on the inner side of the light intensity distribution 121with the inverse peak pattern (to the side where the light intensity islow). By setting the position where the light intensity has the value αto the above-described position (see FIG. 12A), a start point of thecrystal growth can be caused to approximate the center of the lightintensity distribution 120 with the concave pattern including theinverse peak pattern as much as possible, thereby generating crystalgrains with a large particle size.

Furthermore, a crystal nucleus formation position, i.e., a crystalgeneration position can be controlled to an arbitrary two-dimensionalposition by the effect of the inverse peak pattern 121. The incidentlight beams onto the phase modulation element 1 are transmitted from afront surface (front side) of a paper sheet in a direction of a rearsurface (inner side) of the same as indicated by an arrow z in FIG. 12A.This phase modulation element 1 can be manufactured by selecting athickness of, e.g., a quartz glass so as to form a desired phase valuedistribution. A change in thickness of the quartz glass can be formed byselective etching or an FIB.

Moreover, in the phase modulation element having the phase pattern shownin FIG. 12A, the light intensity distribution 121 with the inverse peakpattern is formed at a position where the light intensity becomesminimum in the V-shaped (an alphabetical letter [V] and an inverted [V]are alternately arranged in zigzags) pattern as described with referenceto FIG. 12C due to a phase difference between the two areas, i.e., adifference between the average phase value on the first stripe-like area31 side and the average phase value on the second stripe-like area 32side in the first local area 34 on the border line 33. Since the firstlocal area 13 is linear, a low-light intensity area 36 formed on theprocessed substrate 4 has an acute edge angle, as shown in FIG. 13. Withthis structure, crystal grains 37 can be easily generated in a very widerange. This phenomenon is common to all phase modulation elements whoseborder lines are based on the difference in average phase values.

FIG. 14A is a view schematically showing another structure of the phasemodulation element according to the present invention. Referring to FIG.14A, even in both a line-and-space pattern constituting a firststripe-like area 31 of the phase modulation element 1 and aline-and-space pattern constituting a second stripe-like area 32 of thesame, a duty ratio (width of a line portion/pitch) is 0% at the center,the duty ratio is linearly increased in increments of 5% toward theright-and-left peripheral direction, and the duty ratio is 50% (a totalof 11 steps) on the both sides. It is to be noted that a size of oneside of a phase modulation element block as a unit in the phasemodulation element shown in FIG. 14A is, e.g., 10 μm in a directionindicated by an arrow x and 5 μm in a direction indicated by an arrow yin terms of values converted to the image formation surface.

In the line-and-space pattern of the first stripe-like area 31, eachshaded line portion has a first phase value φ1 (e.g., 90 degrees) andeach non-shaded space portion shown as a space has a second phase valueφ2 (e.g., zero degree). On the other hand, the line-and-space pattern ofthe second stripe-like area 32 is a phase distribution that each shadedline portion has a third phase value φ3 (e.g., −90 degrees) and eachnon-shaded space portion shown as a space has a second phase value φ2(e.g., zero degree).

That is, the phase modulation element 1 shown in FIGS. 14A and 14B has astructure that the first stripe-like area 31 that a superficial contentof an area having a phase value of 90° is gradually increased from thecenter along the arrow x and the second stripe-like area 32 that asuperficial content of an area having a phase value of −90° is graduallyincreased from the center along the arrow x are connected with eachother along a border line 33.

In this manner, in the phase modulation element 1 shown in FIGS. 14A and14B, the first stripe-like area 31 and the second stripe-like area 32are configured to have substantially the same light intensitydistributions which are formed in accordance therewith. In a first localarea 34 on the border line 33 corresponding to a part where the lightintensity of the light intensity distribution is small, an average phasevalue (e.g., approximately 45 degrees) on the first stripe-like area 31side is substantially different from an average phase value (e.g.,approximately −45 degrees) on the second stripe-like area 32 side. Onthe other hand, in a second local area 35 on the border line 33corresponding to a part where the light intensity of the light intensitydistribution is large, an average phase value (e.g., approximately zerodegree) on the first stripe-like area 31 side is substantially equal toan average phase value (e.g., approximately zero degree) on the secondstripe-like area 32 side. The incident light beams onto the phasemodulation element 1 are transmitted from a front surface (front side)of a paper sheet in a direction of a rear surface (inner side) of thesame as indicated by an arrow z in FIG. 14A. This phase modulationelement 1 can be readily manufactured by selecting a thickness of, e.g.,a quartz glass so as to form a desired phase value distribution. Achange in thickness of the quartz glass can be formed by selectiveetching or an FIB.

As described above, according to the phase modulation element shown inFIGS. 14A and 14B, such a light intensity distribution with a concavepattern as shown in FIG. 14B can be obtained in a direction along whichthe phase varies in each of the first stripe-like area 31 and the secondstripe-like area 32 sufficiently distanced from the border line 33 likethe phase modulation element described in connection with FIG. 12A.

FIG. 15A is a schematic view showing in a contour map a light intensitydistribution obtained in the phase modulation element depicted in FIG.14A, FIG. 15B shows a light intensity distribution along the line A-A inFIG. 15A, and FIG. 15C shows a light intensity distribution along theborder line B-B in FIG. 15A, respectively. It is to be noted that animage side numerical aperture NA of the image formation optical system 3(see FIG. 3A) is set to 0.13 and an illumination sigma value (numericalaperture of the illumination system/object side numeral aperture of theimage formation optical system 3) is set to 0.43.

Comparing the FIG. 15B light intensity distribution along the line A-Ain FIG. 15A with the FIG. 15C light intensity distribution along theline B-B in FIG. 15A, it can be understood that a drop in lightintensity which has an inverse peak pattern shape is formed at a partwhere the light intensity is small corresponding to a first local area34. That is, it can be recognized that the light intensity distributionwith a concave pattern suitable for crystallization and an inverse peakpattern that a light intensity is smaller than a threshold value α isactually obtained by irradiating the processed substrate with laserbeams by using the phase modulation element having the phase valuepattern shown in FIG. 14A.

FIG. 16A is a view schematically showing still another structure of thephase modulation element according to the present invention. Referringto FIG. 16A, even in both a line-and-space pattern constituting a firststripe-like area 31 of the phase modulation element 1 and aline-and-space pattern constituting a second stripe-like area 32 of thesame, a duty ratio (width of a line portion/pitch) is 50% (a total of 11steps) and fixed over the entire patterns.

In the line-and-space pattern of the first stripe-like area 31, a phasevalue φ1 of the line portion is closest to a phase of the space portionat the center thereof, a phase value φ11 of the line portion on each ofthe both sides is farthest from the phase of the space portion, and thephase value of the line portion monotonously varies between these areas.Specifically, the phase value φ1 is zero degree, a phase value φ2 is25.9 degrees, a phase value φ3 is 36.9 degrees, a phase value φ4 is 45.6degrees, a phase value φ5 is 53.2 degrees, a phase value φ6 is 60.0degrees, a phase value φ7 is 66.5 degrees, a phase value φ8 is 72.6degrees, a phase value φ9 is 78.5 degrees, a phase value φ10 is 84.3degrees, and the phase value φ11 is 90.0 degrees.

On the other hand, in the line-and-space pattern of the secondstripe-like area 32, a phase value φ-1 of the line portion is closest toa phase of the space portion at the center thereof, a phase value φ-11of the line portion on each of the both sides is farthest from the phaseof the space portion, and the phase value of the line portionmonotonously varies between these areas. Specifically, the phase valueφ-1 is zero degree, a phase value φ-2 is 25.9 degrees, a phase value φ-3is 36.9 degrees, a phase value φ-4 is 45.6 degrees, a phase value φ-5 is53.2 degrees, a phase value φ-6 is 60.0 degrees, a phase value φ-7 is66.5 degrees, a phase value φ-8 is 72.6 degrees, a phase value φ-9 is78.5 degrees, a phase value φ-10 is 84.3 degrees, and the phase valueφ-11 is −90.0 degrees. However, both in the line-and-space patternconstituting the first stripe-like area 31 and the line-and-spacepattern constituting the second stripe-like area 32, the phase values ofthe respective space portion are all zero degree.

It is to be noted that a size of one side of a phase modulation elementblock as a unit in the phase modulation element shown in FIG. 16A is,e.g., 10 μm in a direction indicated by an arrow x and 5 μm in adirection indicated by an arrow y in terms of values converted to theimage formation surface.

In the phase modulation element shown in FIGS. 16A and 16B, the firststripe-like area 31 and the second stripe-like area 32 are configured tohave substantially the same light intensity distributions which areformed in accordance therewith. In this phase modulation element, anaverage phase value (e.g., approximately 45 degrees) on the firststripe-like area 31 side is substantially different from an averagephase value (e.g., approximately −45 degrees) on the second stripe-likearea 32 side in a first local area 34 on a border line 33 correspondingto a part where the light intensity in the light intensity distributionis small. On the other hand, in a second local area 35 on the borderline 33 corresponding to a part where the light intensity in the lightintensity distribution is large, an average phase value (e.g.,approximately zero degree) on the first stripe-like area 31 side issubstantially equal to an average phase value (e.g., approximately zerodegree) on the second stripe-like area 32 side. The light beams enteringthe phase modulation element 1 are transmitted from a front surface(front side) of a paper sheet in a direction of a rear surface (innerside) of the same as indicated by an arrow z in FIG. 16A. This phasemodulation element 1 can be manufactured by selecting a thickness of,e.g., a quartz glass so as to form a desired phase value distribution. Achange in thickness of the quartz glass can be formed by selectiveetching or an FIB.

As described above, according to the phase modulation element shown inFIGS. 16A and 16B, there is obtained such a light intensity distributionwith a concave pattern as shown in FIG. 12B in a direction along whichthe phase varies in each of the first stripe-like area 31 and the secondstripe-like area 32 sufficiently distanced from the border line 33 likethe phase modulation element described above with reference to FIG. 12A.Moreover, a drop in light intensity which has an inverse peak patternshape with a small light intensity corresponding to the first local area34 is formed along the border line 33 as shown in FIG. 12C. As a result,it is possible to obtain the light intensity distribution with a concavepattern suitable for crystallization and an inverse peak pattern thatthe light intensity is smaller than a threshold value α.

FIG. 17A shows in a contour map a light intensity distribution obtainedin the phase modulation element depicted in FIG. 16A, FIG. 17B shows alight intensity distribution along the line A-A in FIG. 17A, and FIG.17C shows a light intensity distribution along the line B-B in FIG. 17A,respectively. It is to be noted that an image side numerical aperture NAof the image formation optical system 3 is set to 0.13 and anillumination sigma value is set to 0.43.

Comparing the FIG. 17B light intensity distribution along the line A-Ain FIG. 17A with the FIG. 17C light intensity distribution along theline B-B in FIG. 17A parallel with the border line 33, it can beunderstood that a drop in light intensity with an inverse peak patternshape is formed at a part where the light intensity is smallcorresponding to the first local area 34. That is, it can be recognizedthat a light intensity distribution with a concave pattern suitable forcrystallization and an inverse peak pattern that the light intensity issmaller than a threshold value α is actually obtained by irradiating theprocessed substrate with the laser beams by using the phase modulationelement having the phase value pattern shown in FIG. 16A.

FIG. 18A is a view schematically showing yet another structure of thephase modulation element according to the present invention. Referringto FIG. 18A, to the phase modulation element 1 are provided astripe-like area 41 which has a predetermined phase distribution andextends along a direction indicated by an arrow x which is a directionalong which the phase varies and isolated areas 42 each of which has aphase value substantially different from that of the periphery inaccordance with a part where the light intensity is small in a lightintensity distribution formed by the effect of the stripe-like area 41.The isolated area 42 is an area which has an optically smaller size thana radius of a unit range C optically corresponding to the point spreaddistribution range R of the image formation optical system 3 and has alarge phase difference.

By using the phase modulation element shown in FIG. 18A, a lightintensity of light beams which are transmitted through an area separatedfrom the isolated area 42 by a predetermined distance in a directionindicated by an arrow y varies with a linearly falling gradient(characteristics that the light intensity becomes maximum at anintermediate position of the isolated areas 42 and the light intensityis gradually decreased toward a position separated from the isolatedareas 42 by a predetermined distance in the direction indicated by anarrow y) in a direction indicated by an arrow x, the light intensityhaving a minimum value at a position separated from the isolated areas42 by a predetermined distance in the direction indicated by the arrow yand the light intensity having a maximum value in the vicinity of anintermediate position between the isolated areas 42 in a direction alongwhich the phase varies, as shown in FIG. 18B. In other words, there isobtained a light intensity distribution with a concave pattern havingthe V-shaped (an alphabetical letter [V] and an inverted [V] arealternately arranged in zigzags) conformation.

As to the light intensity of the light beams in the direction indicatedby the arrow x transmitted through the isolated areas 42, a drop inlight intensity with an inverse peak pattern shape including a partwhere the light intensity is locally small is formed at the part wherethe light intensity is small corresponding to each isolated area 42 bythe effect of the isolated area 40 (since a phase value of each isolatedarea 42 is substantially different from a phase value of the peripherythereof) as shown in FIG. 18C when the phase modulation element depictedin FIG. 18A is used.

In regard to the phase distribution of the phase modulation element 1 toobtain a V-shaped light distribution pattern shown in FIG. 18B, using,e.g., the pattern shown in FIG. 11A can suffice. The light beamsentering the phase modulation element 1 are transmitted from a frontsurface (front side) of a paper sheet in a direction of a rear surface(inner side) of the same as indicated by an arrow z in FIG. 18A. Thisphase modulation element 1 can be manufactured by selecting a thicknessof, e.g., a quartz glass so as to form a desired phase valuedistribution. A change in thickness of the quartz glass can be formed byselective etching or an FIB.

As described above, by using the phase modulation element shown in FIG.18A, there is obtained a combined light intensity distribution resultingfrom the light intensity distribution 181 with a concave pattern having,e.g., the V-shaped (an alphabetical letter [V] and an inverted [V] arealternately arranged in zigzags) and the light intensity distribution182 with an inverse peak pattern including a part where the lightintensity is locally small in the part where the light intensity issmall in this light intensity distribution 181 with the concave pattern,i.e., a combined light intensity distribution with the concave patternand the inverse peak pattern including the part where the lightintensity is locally small shown in FIG. 18C.

As a result, a start point of the crystal growth can be caused toapproximate the center of the light intensity distribution having thepart where the light intensity is locally small as much as possible,thereby generating crystal grains with a large particle size. Moreover,a crystal generation position can be controlled to an arbitrarytwo-dimensional position. Additionally, it is possible to effectcrystallization that the lateral growth with a large particle size isachieved by positioning the inverse peak pattern 182 including the partwhere the light intensity is locally small to, e.g., a seed crystalposition in order to carry out crystallization. The isolated area 42 isnot restricted to a square shape, and any shape such as a circular shapeor a triangular shape can be used.

FIG. 19A is a view schematically showing a further structure of thephase modulation element according to the present invention. Referringto FIG. 19A, in a line-and-space pattern constituting a stripe-like area41 of the phase modulation element 1, a duty ratio (width of a lineportion/pitch) is 100% at the center thereof, the duty ratio is linearlydecreased 5% at a time toward the periphery, and the duty ratio is 50%on each of the both sides.

In the phase modulation element shown in FIG. 19A, each shaded lineportion has a first phase value φ1 (e.g., 90 degrees), each non-shadedspace portion shown as a space has a second phase value φ2 (e.g., zerodegree), and each isolated area 42 has a third phase value φ3 (e.g., 225degrees). As apparent from FIG. 19A, each isolated area 42 is arrangedin accordance with a part where the light intensity is small in a lightintensity distribution formed by the effect of the stripe-like area 41,and has a phase value substantially different from that of theperiphery. The light beams entering the phase modulation element 1 aretransmitted from a front surface (front side) of a paper sheet in adirection of a rear surface (inner side) of the same as indicated by anarrow z in FIG. 19A. This phase modulation element 1 can be readilymanufactured by selecting a thickness of, e.g., a quartz glass so as toform a desired phase value distribution. A change in thickness of thequartz glass can be formed by selective etching or an FIB.

By using the phase modulation element shown in FIG. 19A, the lightintensity of the light beams transmitted through an area separated fromeach isolated area 42 by a predetermined distance in a directionindicated by an arrow y varies with a linearly falling gradient(characteristics that the light intensity becomes maximum at anintermediate position of the isolated areas 42 and the light intensityis gradually decreased toward a position separated from the isolatedareas 42 by a predetermined distance in the direction indicated by thearrow y) in a direction indicated by an arrow x, the light intensityhaving a minimum value at a position separated from the isolated areas42 by a predetermined distance in the direction indicated by the arrow yand the light intensity having a maximum value in the vicinity of anintermediate position between the isolated areas 42 in parallel with adirection along which the phase values as shown in FIG. 19B. That is,there is obtained a light intensity distribution with a concave patternhaving a V-shaped (an alphabetical letter [V] and an inverted [V] arealternately arranged in zigzags) conformation. Additionally, a drop inlight intensity having an inverse peak pattern shape including a partwhere the light intensity is locally small is formed at the part wherethe light intensity is small corresponding to each isolated area along across section including the isolated areas 42 as shown in FIG. 19C. As aresult, it is possible to obtain a light intensity distribution with aconcave pattern suitable for crystallization and an inverse peak patternincluding a part where the light intensity is locally small.

FIG. 20A shows a contour map of a light intensity distribution obtainedin the phase modulation element depicted in FIG. 19A, FIG. 20B shows alight intensity distribution along the line A-A in FIG. 20A, and FIG.20C shows a light intensity along the line B-B in FIG. 20A,respectively. It is to be noted that an image side numerical aperture NAof the image formation optical system 3 is set to 0.13 and anillumination sigma value is set to 0.43.

Comparing the FIG. 20B light intensity distribution along the line A-Ain FIG. 20A with the FIG. 20C light intensity distribution along theline B-B in FIG. 20A parallel with the cross section including theisolated areas 42, it can be understood that a drop in light intensityhaving an inverse peak pattern shape which includes a part where thelight intensity is locally small is formed at the part where the lightintensity is small corresponding to each isolated area 42. That is, itcan be recognized that a light intensity distribution with a concavepattern suitable for crystallization and an inverse peak pattern thatthe light intensity is smaller than a threshold value α is actuallyobtained by irradiating the processed substrate with laser beams byusing the phase modulation element having the phase value pattern shownin FIG. 20A.

FIG. 21A is a view schematically showing a still further structure ofthe phase modulation element according to the present invention.Referring to FIG. 21A, in a pattern constituting a first stripe-likearea 31 of the phase modulation element 1, each shaded rectangular areahas a phase value of, e.g., 90 degrees, and a non-shaded area shown as aspace has a phase value of, e.g., zero degree. On the other hand, in apattern constituting a second stripe-like area 32, each shadedrectangular area has a phase value of, e.g., −90 degrees, and anon-shaded area shown as a space has a phase value of, e.g., zerodegree.

The first stripe-like area 31 and the second stripe-like area 32 areconfigured to have substantially the same light intensity distributionswhich are formed in accordance therewith.

The light beams entering the phase modulation element 1 are transmittedfrom a front surface (front side) of a paper sheet in a direction of arear surface (inner side) of the same as indicated by an arrow z in FIG.21A. This phase modulation element 1 can be readily manufactured byselecting a thickness of, e.g., a quartz glass so as to form first andsecond phase values φ1 and φ2. A change in thickness of the quartz glasscan be formed by selective etching or an FIB.

In the phase modulation element shown in FIG. 21A, an average phasevalue (e.g., approximately 45 degrees) on the first stripe-like area 31side is substantially different from an average value (e.g.,approximately −45 degrees) on the second stripe-like area 32 side in afirst local area 34 defined on a border line 33 corresponding to a partwhere the light intensity in the light intensity distribution is small.On the other hand, in a second local area 35 defined on the border line33 corresponding to a part where the light intensity in the lightintensity distribution is large, an average phase value (e.g.,approximately zero degree) on the first stripe-like area 31 side issubstantially equal to an average phase value (e.g., approximately zerodegree) on the second stripe-like area 32 side.

By using the phase modulation element shown in FIG. 21A, the lightintensity of the light beams passing through an area (cross sectionalong the line A-A) separated from the border line 33 by a predetermineddistance in a direction indicated by an arrow y varies with a linearlyfalling gradient (characteristics that the light intensity becomesmaximum at a position separated from the second local area 35 by apredetermined distance in the direction indicated by the arrow y and thelight intensity is gradually decreased toward a position separated fromthe first local area 34 by a predetermined distance in the directionindicated by the arrow y) in a direction indicated by an arrow x, thelight intensity having a maximum value at a position separated from thesecond local area 35 by a predetermined distance in the directionindicated by the arrow y and the light intensity having a minimum valueat a position separated from the first local area 34 by a predetermineddistance in the direction indicated by the arrow y, as shown in FIG.21B. That is, there is obtained a light intensity distribution with aconcave pattern having a V-shaped (an alphabetical letter [V] and aninverted [V] are alternately arranged in zigzags) conformation. Further,the light intensity of the light beams passing along the border line 33,i.e., the cross section including the first local area 34 and the secondlocal area 35 takes a maximum value in an area corresponding to thesecond local area 35, and takes a minimum value in an area correspondingto the first local area 34. It is to be noted that a drop in lightintensity having an inverse peak pattern shape which includes a partwhere the light intensity is locally small is formed in the areacorresponding to the first local area 34. That is, there can be obtaineda light intensity distribution with a concave pattern suitable forcrystallization and an inverse peak pattern including a part where thelight intensity is locally small.

FIG. 22A is a view schematically showing a yet further structure of thephase modulation element according to the present invention. Referringto FIG. 22A, in a pattern constituting a stripe-like area 41 of thephase modulation element 1, each shaded rectangular area has a phasevalue of, e.g., 90 degrees, and a non-shaded area shown as a space has aphase value of, e.g., zero degree. Furthermore, each isolated area 42having a phase value (e.g., 225 degrees) substantially different fromthat of the periphery is provided in accordance with a part where alight intensity is small in a light intensity distribution formed by theeffect of the stripe-like area 41. As apparent from FIG. 22A, eachisolated area 42 is arranged in accordance with the part where the lightintensity is small in the light intensity distribution formed by theeffect of the stripe-like area 41, and has a phase value substantiallydifferent from that of the periphery. The light beams entering the phasemodulation element 1 are transmitted from a front surface (front side)of a paper sheet in a direction of a rear surface (inner side) of thesame as indicated by an arrow z in FIG. 22A. This phase modulationelement 1 can be readily manufactured by selecting a thickness of, e.g.,a quartz glass so as to form a desired phase value distribution. Achange in thickness of the quartz glass can be formed by selectiveetching or an FIB.

By using the phase modulation element shown in FIG. 22A, the lightintensity of the light beams which pass through an area separated fromeach isolated area 42 by a predetermined distance in a directionindicated by an arrow y varies with a linearly falling gradient(characteristics that the light intensity becomes maximum at anintermediate position of the isolated areas 42 and the light intensityis gradually decreased toward a position separated from each isolatedarea 42 by a predetermined distance in the direction indicated by thearrow y) in a direction indicated by an arrow x with the light intensityhaving a minimum value at a position separated from each isolated area42 by a predetermined distance in the direction indicated by the arrow yand the light intensity having a maximum value in the vicinity of theintermediate position between the isolated areas 42 in parallel with adirection along which the phase varies, as shown in FIG. 22B. That is,there is obtained a light intensity distribution with a concave patternhaving a V-shaped (an alphabetical letter [V] and an inverted [V] arealternately arranged in zigzags) conformation. Furthermore, a drop inlight intensity with an inverse peak pattern shape including a partwhere the light intensity is locally small is formed at the part wherethe light intensity is small corresponding to each isolated area 42, asshown in FIG. 22C. As a result, it is possible to obtain a lightintensity distribution with a concave pattern suitable forcrystallization and an inverse peak pattern including the part where thelight intensity is locally small.

FIG. 23A is a view schematically showing another structure of the phasemodulation element according to the present invention. Referring to FIG.23A, in a pattern constituting a stripe-like area 41 of the phasemodulation element 1, each shaded line portion has a phase value of,e.g., 90 degrees, and each non-shaded space portion shown as a space hasa phase value of, e.g., zero degree, and isolated areas 42 each having aphase value (e.g., 225 degrees) substantially different from that of theperiphery are provided in accordance with parts having the small lightintensity in a light intensity distribution formed by the effect of thestripe-like area 41. The light beams entering the phase modulationelement 1 are transmitted from a front surface (front side) of a papersheet in a direction of a rear surface (inner side) of the same asindicated by an arrow z in FIG. 23A. This phase modulation element 1 canbe readily manufactured by selecting a thickness of, e.g., a quartzglass so as to form a desired phase value distribution. A change inthickness of the quartz glass can be formed by selective etching or anFIB.

By using the phase modulation element shown in FIG. 23A, a lightintensity of the light beams passing through an area separated from eachisolated area 42 by a predetermined distance in a direction indicated byan arrow y varies with a linearly falling gradient (characteristics thatthe light intensity becomes maximum at an intermediate position of theisolated areas 42 and the light intensity is gradually decreased towarda position separated from each isolated area 42 by a predetermineddistance in the direction indicated by an arrow y) in a directionindicated by an arrow x, the light intensity having a minimum value at aposition separated from each isolated area 42 by a predeterminedposition in the direction indicated by the arrow y and the lightintensity having a maximum value in the vicinity of the intermediateposition between the isolated areas 42 in parallel with a directionalong which the phase varies, as shown in FIG. 23B. That is, there isobtained a light intensity distribution with a concave pattern having aV-shaped (an alphabetical letter [V] and an inverted [V] are alternatelyarranged in zigzags) conformation. Moreover, a drop in light intensitywith an inverse peak pattern shape including a part where the lightintensity is locally small is formed at the part where the lightintensity is small corresponding to each isolated area 42 along a crosssection including each isolated area 42. As a result, there can beobtained a light intensity distribution with a concave pattern suitablefor crystallization and an inverse peak pattern including the part wherethe light intensity is locally small.

FIG. 24A is a view schematically showing still another structure of thephase modulation element according to the present invention. Referringto FIG. 24A, in a pattern constituting a stripe-like area 41 of thephase modulation element 1, a phase value of each shaded line portionvaries in a range between, e.g., zero degree and 90 degrees inaccordance with each line portion, and each non-shaded space portionshown as a space has a phase value of, e.g., zero degree. It is to benoted that each isolated area 42 having a phase value (e.g., 225degrees) substantially different from that of the periphery is providedin accordance with a part having a small light intensity in a lightintensity distribution formed by the effect of the stripe-like area 41.The light beams entering the phase modulation element 1 are transmittedfrom a front surface (front side) of a paper sheet in a direction of arear surface (inner side) of the same as indicated by an arrow z in FIG.24A. This phase modulation element 1 can be readily manufactured byselecting a thickness of, e.g., a quartz glass so as to form a desiredphase value distribution. A change in thickness of the quartz glass canbe formed by selective etching or an FIB.

By using the phase modulation element shown in FIG. 24A, a lightintensity of the light beams passing through an area separated from eachisolated area 42 by a predetermined distance in a direction indicated byan arrow y varies with a linearly falling gradient (characteristics thatthe light intensity becomes maximum at an intermediate position of theisolated areas 42 and the light intensity is gradually decreased towarda position separated from each isolated area 42 by a predetermineddistance in the direction indicated by the arrow y) in a directionindicated by an arrow x, the light intensity having a minimum value at aposition separated from each isolated area 42 by a predetermineddistance in the direction indicated by the arrow y and the lightintensity having a maximum value in the vicinity of the intermediateposition between the isolated areas 42 in parallel with a directionalong which the phase varies, as shown in FIG. 24B. That is, there isobtained a light intensity distribution with a concave pattern having aV-shaped (an alphabetical character [V] and an inverted [V] arealternately arranged in zigzags) conformation. Furthermore, a drop inlight intensity with an inverse peak pattern shape including a partwhere the light intensity is locally small is formed at the part wherethe light intensity is small corresponding to each isolated area 42 asshown in FIG. 24C. As a result, there can be obtained a light intensitydistribution with a concave pattern suitable for crystallization and aninverse peak pattern including the part where the light intensity islocally small.

FIG. 25A is a view schematically showing yet another structure of thephase modulation element according to the present invention. Referringto FIG. 25A, in a pattern constituting a stripe-like area 41 of thephase modulation element 1, each shaded stripe-like area has a phasevalue of, e.g., 90 degrees, each non-shaded area shown as a space has aphase value of, e.g., zero degree, and isolated areas 42 each having aphase value (e.g., 225 degrees) substantially different from that of theperiphery are provided in accordance with parts each having a smalllight intensity in a light intensity distribution formed by the effectof the stripe-like area 41. The light beams entering the phasemodulation element 1 are transmitted from a front surface (front side)of a paper sheet in a direction of a rear surface (inner side) of thesame as indicated by an arrow z in FIG. 25A. This phase modulationelement 1 can be readily manufactured by selecting a thickness of, e.g.,a quartz glass so as to form first and second phase values φ1 and φ2. Achange in thickness of the quartz glass can be formed by selectiveetching or an FIB.

By using the phase modulation element shown in FIG. 25A, a lightintensity of the light beams passing through an area separated from eachisolated area 42 by a predetermined distance in a direction indicated byan arrow y varies with a linearly falling gradient (characteristics thatthe light intensity becomes maximum at an intermediate position of theisolated areas 42 and the light intensity is gradually decreased towarda position separated from each isolated area 42 by a predetermineddistance in the direction indicated by the arrow y) in a directionindicated by an arrow x, the light intensity having a minimum value atthe position separated from each isolated area 42 by a predetermineddistance in the direction indicated by the arrow y and the lightintensity having a maximum value in the vicinity of the intermediateposition between the isolated areas 42 in parallel with a directionalong which the phase varies, as shown in FIG. 25B. That is, there isobtained a light intensity distribution with a concave pattern having aV-shaped (an alphabetical letter [V] and an inverted [V] are alternatelyarranged in zigzags) conformation. Moreover, as shown in FIG. 25C, adrop in light intensity with an inverse peak pattern shape including apart where the light intensity is locally small is formed at the partwhere the light intensity is small corresponding to each isolated area42 along a cross section including each isolated area 42. As a result,there can be obtained a light intensity distribution with a concavepattern suitable for crystallization and an inverse peak patternincluding the parts where the light intensity is locally small.

It is to be noted that the example that the phase modulation element 1takes the finite number of phase values are described in the abovevarious embodiments but the phase value may continuously vary. Forexample, when interpolation processing is carried out by using anarbitrary method in order to substitute the stepped distribution of thephase modulation element 1 in the foregoing embodiments for a smoothcurved surface, the equivalent advantages can be obtained.

Additionally, the phase modulation element 1 can be realized by anirregular shape corresponding to a phase value by using a technique tomanufacture a regular phase shift mask.

Further, the phase modulation element 1 can be also realized by using adistribution of refractive indices of a material as well as theirregular shape.

Furthermore, the phase modulation element 1 such as a liquid crystalelement or a micro mirror device which can vary a phase modulationquantity may be realized.

Moreover, in the foregoing embodiments, the light intensity distributioncan be calculated on a design stage, but it is desirable to observe andconfirm the light intensity distribution on an actual processed surface.In order to realize this, it is good enough to magnify the processedsurface of the processed substrate 4 by using the optical system andinput a result by utilizing an imaging element such as a CCD.Incidentally, if the light beams to be used are ultraviolet rays, theoptical system including a CCD element and others may be possiblyrestricted in sensitivity or photoelectric conversion efficiency.Therefore, a fluorescent screen may be provided on the processed surfaceonly during observation in order to convert the light beams into visiblelight beams. Additionally, although the concrete structural examples ofthe phase modulation element 1 have been described in connection withthe foregoing embodiments, various kinds of modifications of thestructure of the phase modulation element 1 can be carried out withinthe scope of the present invention.

FIGS. 26A to 26E are process cross-sectional views showing steps tomanufacture an electronic device in an area (processed surface)crystallized by using the crystallization apparatus according to thisembodiment.

As shown in FIG. 26A, there is prepared a processed substrate 4 havingan underlying film 81 (e.g., SiN having a film thickness of 50 nm and anSiO₂ laminated film having a film thickness of 100 nm) and an amorphoussemiconductor film 82 (e.g., Si, Ge, SiGe and others each having a filmthickness of approximately 50 nm to 200 nm) formed on an insulatedsubstrate 80 (e.g., alkali glass, quartz glass, plastic or polyimide) byusing chemical vapor deposition or a sputtering method.

Subsequently, all or a part of a surface of the amorphous semiconductorfilm 82, e.g., a predetermined area is irradiated with laser beams 83(e.g., KrF excimer laser beams or an XeCl excimer laser beams) by usingthe crystallization apparatus shown in FIG. 1 through the phasemodulation element 1 according to the above-described various kinds ofconformations, e.g., the phase modulation element 1 shown in FIG. 9C.

Therefore, a polycrystal semiconductor film or a single-crystallizedsemiconductor film 84 having a crystal with a large particle size isgenerated as shown in FIG. 26B.

Then, as shown in FIG. 26C, the polycrystal semiconductor film or thesingle-crystallized semiconductor film 84 is processed into anisland-shaped semiconductor film 85 which becomes an area used to form,e.g., a thin film transistor by using a photolithography technique, andan SiO₂ film having a film thickness of 20 nm to 100 nm as a gateinsulating film 86 is formed on a surface of the semiconductor film 85by using, e.g., chemical vapor deposition or a sputtering method.

Further, as shown in FIG. 26D, a gate electrode 87 (e.g., silicide orMoW) is formed on the gate insulating film, impurity ions 88(phosphorous in case of an N channel transistor, and boron in case of aP channel transistor) are implanted with the gate electrode 87 beingused as a mask. Thereafter, although not shown, annealing processing iscarried out in a nitrogen atmosphere (e.g., one hour at 450° C.), andthe impurities are activated, thereby forming a source area 91 and adrain area 92 in the island-shaped semiconductor film 85.

Then, as shown in FIG. 26E, for example, an interlayer insulating film89 is formed, contact holes are formed, and a source electrode 93 and adrain electrode 94 connected with a source 91 and a drain 92 which areconnected through a channel 90 are formed.

In the above-described steps, a channel 90 is formed in accordance witha position of a crystal with a large particle size of the polycrystalsemiconductor film or the single-crystallized semiconductor film 84generated in the steps shown in FIGS. 26A and 26B.

Based on the above-described steps, a thin film transistor (TFT) can beformed to the polycrystal transistor or the single-crystallizedsemiconductor.

The polycrystal transistor or the single-crystallized transistormanufactured in the steps shown in FIGS. 26A to 26E can be applied to adrive circuit for, e.g., a liquid crystal display (display) or an EL(electroluminescence) display, or an integrated circuit for a memory(SRAM or DRAM) or a CPU.

A description will now be given as to an embodiment that a base materialincluding an area crystallized by using the crystallization apparatusaccording to this embodiment is applied to a display apparatus, e.g., aliquid crystal display.

A method for forming a display apparatus including TFTs will now bedescribed hereinafter.

FIGS. 26 and 28 show a display apparatus, e.g., an active matrix typeliquid crystal display. The display apparatus 220 will be referred to asa liquid crystal display hereinafter.

First, the liquid crystal display 220 will be described. The liquidcrystal display 220 comprises a pair of front and rear transparent basesubstances 221 and 222, a liquid crystal layer 223, pixel electrodes224, scanning wirings 225, signal wirings 226, an opposed electrode 227,TFTs 230 and others.

As the pair of transparent base substances 221 and 222, a pair of glasssheets can be used, for example. These transparent base substances 221and 222 are joined through a non-illustrated frame-shaped sealingmaterial. The liquid crystal layer 223 is provided to an area surroundedby the sealing material between the pair of transparent base substances221 and 222.

On the inner surface of one of the pair of transparent base substances221 and 222, e.g., the transparent base substance 222 on the rear sideare provided a plurality of pixel electrodes 224 provided in a matrixform in a row direction and a column direction, a plurality of TFTs 230electrically connected with the plurality of pixel electrodes 224, andscanning wirings 225 and signal wirings 226 which are electricallyconnected with the plurality of TFTs 230.

The scanning wirings 225 are provided along the row direction of thepixel electrodes 224. One end of each of the scanning wirings 225 isconnected with each of a plurality of scanning wiring terminals (notshown) provided at an edge portion of the rear transparent basesubstance 222 on one side. A plurality of scanning wiring terminals arerespectively connected with a scanning line drive circuit 241.

On the other hand, the signal wirings 226 are provided along the columndirection of the pixel electrodes 24. One end of each of these signalwirings 226 is connected with each of a plurality of signal wiring 226terminals (not shown) provided at a one end edge portion of the reartransparent base substance 222. The plurality of signal wiring 226terminals are respectively connected with a signal line drive circuit242. The scanning line drive circuit 241 and the signal line drivecircuit 242 are respectively connected with a liquid crystal controller243. The liquid crystal controller 243 receives an image signal and asynchronization signal supplied from, e.g., the outside, and generates apixel picture signal Vpix, a vertical scanning control signal YCT and ahorizontal scanning control signal XCT.

One film-like transparent opposed electrode 227 which is opposed to theplurality of pixel electrodes 224 is provided on an inner surface of thetransparent base substance 221 on a front side which is the othertransparent base substance. Furthermore, on the inner surface of thetransparent base substance 221 on the front side may be provided a colorfilter according to a plurality of pixel portions at which the pluralityof pixel electrodes 224 are opposed to the opposed electrode 227, and alight shielding film in accordance with each area between the pixelportions.

A non-illustrated deflecting plate is provided on the outer side of thepair of transparent base substances 221 and 222. Moreover, in thetransmission type liquid crystal display 220, a non-illustrated surfacelight source is provided on the rear side of the rear transparent basesubstance 222. It is to be noted that the liquid crystal display 220 maybe of a reflection type or a semi-transmission reflection type.

As described above, in the crystallization apparatus and thecrystallization method according to the present invention, the phasemodulation element has a phase distribution based on a phase modulationunit which is optically smaller than a radius of a point spreaddistribution range R of the image formation optical system. Therefore,by appropriately changing a combination of a plurality of unit vectorsin a unit range optically corresponding to the point spread distributionrange R of the image formation optical system, a light intensitydistribution to be formed can be analytically controlled in accordancewith a simple calculation. As a result, in the present invention, basedon a light intensity distribution with, e.g., a concave pattern that alight intensity is minimum at the center and the light intensity isincreased toward the periphery, the sufficient lateral growth of acrystal from a crystal nucleus can be realized, and a crystallizedsemiconductor film with a large particle size can be generated.

For example, there is provided a crystallization apparatus comprising: aphase modulation element; an illumination system used to illuminate thephase modulation element; an image formation optical system arranged ina light path between the phase modulation element and a polycrystalsemiconductor film or an amorphous semiconductor film, wherein the phasemodulation element has a phase distribution based on a phase modulationunit which is optically smaller than a radius of a point spreaddistribution range of the image formation optical system, and acrystallized semiconductor film is generated by irradiating thepolycrystal semiconductor film or the amorphous semiconductor film withlight beams having a predetermined light intensity distribution. In thisstructure, the phase modulation element has the phase distribution basedon the phase modulation unit which is optically smaller than the radiusof the point spread distribution range of the image formation opticalsystem. Therefore, by appropriately changing a combination of aplurality of unit vectors in a unit range optically corresponding to thepoint spread distribution range of the image formation optical system, alight intensity distribution to be formed can be analytically controlledin accordance a simple calculation. A crystallized semiconductor filmwith a large particle size can be generated by causing a lateral growthof a crystal from a crystal nucleus based on a light intensitydistribution with, e.g., a concave pattern that a light intensity isminimum at the center and the light intensity is increased toward theperiphery.

Moreover, according to the present invention, there is provided anapparatus comprising: a phase modulation element; an illumination systemused to illuminate the phase modulation element; and an image formationoptical system arranged in a light path between the phase modulationelement and a predetermined surface, wherein the phase modulationelement has a phase distribution based on a phase modulation unit whichis optically smaller than a radius of a point spread distribution rangeof the image formation optical system, and a predetermined lightintensity distribution is formed on the predetermined surface. In thiscase, the light intensity distribution formed on the predeterminedsurface can be likewise analytically controlled in accordance with asimple calculation in an appropriate apparatus other than thecrystallization apparatus.

That is, the phase modulation element has a phase distribution that areashares of a first area having a first phase value and a second areahaving a second phase value vary depending on each position. In thiscase, it is preferable that the phase modulation element has a pluralityof cells each of which is optically smaller than the radius of the pointspread distribution range of the image formation optical system and areashares of the first area and the second area in each cell vary inaccordance with each cell. Alternatively, it is preferable that thephase modulation element has a plurality of pixels each of which isoptically smaller than the radius of the point spread distribution rangeof the image formation optical system, each pixel has a fixed value andthe number of pixels having the same phase value per unit rangeoptically corresponding to the point spread distribution range vary inaccordance with each unit range. Alternatively, it is preferable thatthe phase modulation element has a plurality of stripe-like areas eachhaving a width optically smaller than the radius of the point spreaddistribution range of the image formation optical system, eachstripe-like area has a fixed phase value, and a width of eachstripe-like area varies along a longitudinal direction. Alternatively,it is preferable that the phase modulation element has a line-and-spacepattern having an optically smaller width than the radius of the pointspread distribution range of the image formation optical system, eachline portion has the first phase value, each space portion has thesecond phase value and a ratio of a width of the line portion and awidth of the space portion which are adjacent to each other varies alonga widthwise direction. Additionally, the phase modulation element has acyclic divided area structure, each divided area has a fixed phasevalue, and the phase modulation element has a phase distribution thatthe phase value varies in accordance with each divided area. In thiscase, it is preferable that the phase modulation element has a pluralityof pixels each of which is optically smaller than the radius of thepoint spread distribution range of the image formation optical system,each pixel has a fixed phase value, and the phase value varies inaccordance with each pixel. Alternatively, it is preferable that thephase modulation element has a line-and-space pattern whose width isoptically smaller than the radius of the point spread distribution rangeof the image formation optical system and the phase value varies inaccordance with each line portion. Further, the phase modulation elementhas a first stripe-like area which has a first phase distribution andextends in a direction along which the phase varies and a secondstripe-like area which has a second phase distribution and extends in adirection along which the phase varies, the first stripe-like area andthe second stripe-like area are adjacent to each other with a borderline in the direction along which the phase varies therebetween, and anaverage phase value on the first stripe-like area side is substantiallydifferent from an average phase value on the second stripe-like areaside in a local area on the border line.

In this case, it is preferable that the first stripe-like area and thesecond stripe-like area are configured to have substantially the samelight intensity distributions formed in accordance therewith, an averagephase value on the first stripe-like area side is substantiallydifferent from an average phase value on the second stripe-like areaside in a first local area on the border line corresponding to a partwith a small intensity in the light intensity distribution, and theaverage phase value on the first stripe-like area side is substantiallyequal to the average phase value on the second stripe-like area side ina second local area on the border line corresponding to a part with alarge intensity in the light intensity distribution. Furthermore, it ispreferable that the first stripe-like area and the second stripe-likearea has a line-and-space pattern whose width is optically smaller thanthe radius of the point spread distribution range of the image formationoptical system, each line portion has the first phase value, each spaceportion has the second phase value, and a ratio in width of the lineportion and the space portion which are adjacent to each other variesalong a widthwise direction. Alternatively, it is preferable that thefirst stripe-like area and the second stripe-like area has aline-and-space pattern whose width is optically smaller than the radiusof the point spread distribution range of the image formation opticalsystem, and the phase value varies in accordance with each line portion.Moreover, the phase modulation element comprises isolated areas each ofwhich is optically smaller than the radius of the point spreaddistribution range of the image formation optical system and has a phasevalue substantially different from that of the periphery in accordancewith parts with a small light intensity in a light intensitydistribution to be formed. Additionally, in the first or secondembodiment, it is preferable that the predetermined light intensitydistribution has a light intensity distribution with a concave patternthat the light intensity is increased from a central area having a firstintensity toward the periphery. In this case, it is preferable that thelight intensity distribution with the concave pattern has a distributionthat the light intensity is one-dimensionally increased from the centralarea toward the periphery. Further, it is preferable that thepredetermined light intensity distribution has a light intensitydistribution with an inverse peak pattern that the light intensity issuddenly increased from a second central area having a second lightintensity substantially smaller than the first light intensity towardthe periphery in the vicinity of the central area of the light intensitydistribution with the concave pattern.

Furthermore, according to the present invention, there is provided acrystallization method comprising: illuminating a phase modulationelement having a phase distribution based on a phase modulation unitoptically smaller than a radius of a point spread distribution range ofan image formation optical system; and irradiating a polycrystalsemiconductor film or an amorphous semiconductor film with light beamshaving a predetermined light intensity distribution through the imageformation optical system arranged in a light path between the phasemodulation element and the polycrystal semiconductor film or theamorphous semiconductor film, thereby forming a crystallizedsemiconductor film. In this case, a light intensity distribution to beformed can be analytically controlled in accordance with a simplecalculation like the case of the crystallization apparatus. As a result,a crystallized semiconductor film with a large particle size can begenerated by causing a lateral growth of a crystal from a crystalnucleus based on a light intensity distribution with, e.g., a desiredconcave pattern suitable for crystallization.

Moreover, according to the present invention, there is provided a methodcomprising: illuminating a phase modulation element having a phasedistribution based on a phase modulation unit optically smaller than aradius of a point spread distribution range of an image formationoptical system; and forming a predetermined light intensity distributionon a predetermined surface through the image formation optical systemarranged in a light path between the phase modulation element and thepredetermined surface. In this case, the light intensity distributionformed on the predetermined surface can be also analytically controlledin accordance with a simple calculation in any appropriate method otherthan the crystallization method.

Additionally, according to the present invention, there is provided aphase modulation element having a phase distribution based on a phasemodulation unit with a predetermined size, the phase modulation elementhaving a phase distribution that area shares of a first area having afirst phase value and a second area having a second phase value vary inaccordance with each position. A light intensity distribution with adesired concave pattern suitable for crystallization can be formed byapplying this phase modulation element to, e.g., a crystallizationapparatus. As a result, a crystallized semiconductor film with a largeparticle size can be generated by causing a lateral growth of a crystalfrom a crystal nucleus based on the light intensity distribution withthe desired concave pattern.

Further, it is preferable that the present invention has a plurality ofcells and area shares of the first area and the second area in each cellvary in accordance with each cell. Alternatively, it is preferable thatthe present invention has a plurality of pixels, each pixel has a fixedphase value, and the number of pixels having the same phase value perunit range optically corresponding to the point spread distributionrange varies in accordance with each unit range. Alternatively, it ispreferable that the present invention has a plurality of stripe-likeareas, each stripe-like area has a fixed phase value, and a width ofeach stripe-like area varies along a longitudinal direction.Alternatively, it is preferable that the present invention has aline-and-space pattern, each line portion has the first phase value,each space portion has the second phase value and a ratio in width ofthe line portion and the space portion which are adjacent to each othervaries along a widthwise direction.

Furthermore, according to the present invention, there is provided aphase modulation element having a phase distribution based on a phasemodulation unit with a predetermined size, wherein the phase modulationelement has a cyclic divided area structure, each divided area has afixed phase value, and the phase modulation element has a phasedistribution that the phase value varies in accordance with each dividedarea. In this case, a light intensity distribution with a desiredconcave pattern suitable for crystallization can be formed by applyingthe phase modulation element to, e.g., a crystallization apparatus, anda crystallized semiconductor film with a large particle size can begenerated by causing a lateral growth of a crystal from a crystalnucleus.

Moreover, it is preferable that the present invention has a plurality ofpixels, each pixel has a fixed phase value and the phase value varies inaccordance with each pixel. Alternatively, it is preferable that thepresent invention has a line-and-space pattern and a phase value variesin accordance with each line portion.

Additionally, according to the present invention, there is provided aphase modulation element having a phase distribution based on a phasemodulation unit with a predetermined size, wherein the phase modulationelement has a first stripe-like area which has a first phasedistribution and extends in a direction along which a phase varies and asecond stripe-like area which has a second phase distribution andextends in a direction along which a phase varies, the first stripe-likearea and the second stripe-like area are adjacent to each other with aborder line parallel with the direction along which the phase variestherebetween, and an average phase value on the first stripe-like areaside is substantially different from an average phase value on thesecond stripe-like area side in a local area on the border line. In thiscase, a light intensity distribution with both a desired concave patternsuitable for crystallization and an inverse peak pattern can be formedby applying the phase modulation element to, e.g., a crystallizationapparatus, and a crystallized semiconductor film having a large particlesize can be generated by causing a lateral growth of a crystal from acrystal nucleus.

Further, the first stripe-like area and the second stripe-like area areconfigured to have substantially the same light intensity distributionswhich are formed in accordance therewith, an average phase value on thefirst stripe-like area side is substantially different from an averagephase value on the second stripe-like area side in a first local area onthe border line corresponding to a part where a light intensity in thelight intensity distribution is small, and the average phase value onthe first stripe-like area side is substantially equal to the averagephase value on the second stripe-like area side in a second local areaon the border line corresponding to a part where a light intensity inthe light intensity distribution is large. Furthermore, it is preferablethat the first stripe-like area and the second stripe-like area have aline-and-space pattern, each line portion has a first phase value, eachspace portion has a second phase value, and a ratio in width of the lineportion and the space portion which are adjacent to each other varies ina widthwise direction. Alternatively, it is preferable that the firststripe-like area and the second stripe-like area have a line-and-spacepattern and a phase value varies in accordance with each line portion.

It is to be noted that a processed film, i.e., a base substancemanufactured by using the phase modulation element according to any ofthe embodiments of the present invention has a crystal caused to grow toa predetermined size in the lateral direction from a crystal nucleus,and hence an electronic device configured by using that base substancedemonstrates excellent semiconductor characteristics. Moreover, adisplay apparatus which stably operates can be obtained by using thesame base substance in, e.g., a liquid crystal display panel.

1. A crystallization method comprising: illuminating a phase modulationelement having a phase distribution based on a phase modulation unitwhich is optically smaller than a radius of a point spread distributionrange of an image formation optical system when converted to an imageformation surface; and irradiating a polycrystal semiconductor film oran amorphous semiconductor film with light beams having a predeterminedlight intensity distribution through the image formation optical systemarranged in a light path between the phase modulation element and thepolycrystal semiconductor film or the amorphous semiconductor film,thereby generating a crystallized semiconductor film.
 2. Acrystallization method comprising: illuminating a phase modulationelement having a phase distribution based on a phase modulation unitwhich is optically smaller than a radius of a point spread distributionrange of an image formation optical system when converted to an imageformation surface; and forming a predetermined light intensitydistribution on a predetermined surface through the image formationoptical system arranged in a light path between the phase modulationelement and the predetermined surface.
 3. A phase modulation elementhaving a phase distribution based on a phase modulation unit having apredetermined size, comprising: a first area having a first phase value;and a second area having a second phase value, wherein the phasedistribution is defined by a change in area shares of the first area andthe second area depending on each position.
 4. The phase modulationelement according to claim 3, wherein the phase modulation element has aplurality of cells, and area shares of the first area and the secondarea in each cell vary in accordance with each cell.
 5. The phasemodulation element according to claim 3, wherein the phase modulationelement comprises a plurality of pixels each having a fixed phase value,and the number of pixels having the same phase value per unit rangevaries in accordance with each unit range.
 6. The phase modulationelement according to claim 3, wherein the phase modulation elementcomprises a plurality of stripe-like areas each having a fixed phasevalue, and a width of each stripe-like area varies along a longitudinaldirection.
 7. The phase modulation element according to claim 3, whereinthe phase modulation element has a line-and-space pattern which includesa plurality of line portions each having the first phase value and aplurality of space portions each having the second phase value, and aratio in width of the line portion and the space portion which areadjacent to each other varies along a widthwise direction.
 8. A phasemodulation element having a phase distribution based on a phasemodulation unit having a predetermined size, comprising: a plurality ofdivided areas each having a fixed phase value, wherein each of thedivided areas has a phase distribution that the phase value cyclicallyvaries in accordance with each divided area.
 9. The phase modulationelement according to claim 8, wherein the phase modulation elementcomprises a plurality of pixels each having a fixed phase value, and thephase value of each pixel varies in accordance with each pixel.
 10. Thephase modulation element according to claim 8, wherein the phasemodulation element has a line-and-space pattern, and a the phase valuevaries in accordance with each line portion.
 11. A phase modulationelement having a phase distribution based on a phase modulation unithaving a predetermined size, comprising: a first stripe-like area whichhas a first phase distribution and extends in a direction along which aphase varies; and a second stripe-like area which has a second phasedistribution and extends in the direction along which the phase varies,wherein the first stripe-like area and the second stripe-like area areadjacent to each other with a border line parallel with the directionalong which the phase varies therebetween, and an average phase value onthe first stripe-like area side is substantially different from anaverage phase value on the second stripe-like area side in a local areaon the border line.
 12. The phase modulation element according to claim11, wherein the first stripe-like area and the second stripe-like areaare configured to have substantially the same light intensitydistributions which are formed in accordance therewith, the averagephase value on the first stripe-like area side is substantiallydifferent from the average phase value on the second stripe-like areaside in a first local area on the border line corresponding to a partwhere a light intensity in the light intensity distribution is small,and the average phase value on the first stripe-like area side issubstantially equal to the average phase value on the second stripe-likearea side in a second local area on the border line corresponding to apart where a light intensity in the light intensity distribution islarge.
 13. The phase modulation element according to claim 11, whereinthe first stripe-like area and the second stripe-like area have aline-and-space pattern, each line portion has a first phase value, eachspace portion has a second phase value, and a ratio in width of the lineportion and the space portion which are adjacent to each other variesalong a widthwise direction.
 14. The phase modulation element accordingto claim 12, wherein the first stripe-like area and the secondstripe-like area have a line-and-space pattern, each line portion has afirst phase value, each space portion has a second phase value, and aratio in width of the line portion and the space portion which areadjacent to each other varies along a widthwise direction.
 15. The phasemodulation element according to claim 11, wherein the first stripe-likearea and the second stripe-like area have a line-and-space pattern, andthe phase value of the line portion varies in accordance with each line.16. The phase modulation element according to claim 12, wherein thefirst stripe-like area and the second stripe-like area have aline-and-space pattern, and the phase value of the line portion variesin accordance with each line.
 17. The phase modulation element accordingto claim 3, wherein the phase modulation element comprises isolatedareas each of which has a phase value which is substantially differentfrom that of a periphery in accordance with parts where a lightintensity in a light intensity distribution to be formed is small.
 18. Adevice comprising: a semiconductor film manufactured by acrystallization method, the crystallization method comprising:illuminating a phase modulation element having a phase distributionbased on a phase modulation unit which is optically smaller than aradius of a point spread distribution range of an image formationoptical system when converted to an image formation surface; and forminga predetermined light intensity distribution on a predetermined surfacethrough the image formation optical system arranged in a light pathbetween the phase modulation element and the predetermined surface. 19.A display apparatus comprising: a pair of substrates joined to eachother with a predetermined gap therebetween; an electro-optic materialheld in the gap; an opposed electrode formed on one of the substrates;and a semiconductor thin film which can provide pixel electrodes formedon the other substrate and thin film transistors which drive the pixelelectrodes, wherein the semiconductor thin film is a semiconductor filmcrystallized by irradiating the polycrystal semiconductor film or theamorphous semiconductor film with light beams having a predeterminedlight intensity distribution through a phase modulation element in whicha phase of outgoing light beams relative to incident light beams variesdepending on each position and an image formation optical system.